diff --git a/third_party/unrar/src/crc.cpp b/third_party/unrar/src/crc.cpp
index 1097f4cd00d1..8488e102c28e 100644
--- a/third_party/unrar/src/crc.cpp
+++ b/third_party/unrar/src/crc.cpp
@@ -15,6 +15,7 @@
 #include "rar.hpp"
 
 static uint crc_tables[8][256]; // Tables for Slicing-by-8.
+static bool is_initialized = false;
 
 
 // Build the classic CRC32 lookup table.
@@ -49,10 +50,13 @@ static void InitTables()
 }
 
 
-struct CallInitCRC {CallInitCRC() {InitTables();}} static CallInit32;
-
 uint CRC32(uint StartCRC,const void *Addr,size_t Size)
 {
+  if (!is_initialized) {
+    is_initialized = true;
+    InitTables();
+  }
+
   byte *Data=(byte *)Addr;
 
   // Align Data to 8 for better performance.
diff --git a/third_party/unrar/src/errhnd.cpp b/third_party/unrar/src/errhnd.cpp
index e862bb3a7566..3dd92a9cb88a 100644
--- a/third_party/unrar/src/errhnd.cpp
+++ b/third_party/unrar/src/errhnd.cpp
@@ -1,10 +1,11 @@
-#include "rar.hpp"
-
-ErrorHandler::ErrorHandler()
-{
-  Clean();
-}
+// NOTE(vakh): The process.h file needs to be included first because "rar.hpp"
+// defines certain macros that cause symbol redefinition errors
+#if defined(UNRAR_NO_EXCEPTIONS)
+#include "base/logging.h"
+#include "base/process/process.h"
+#endif  // defined(UNRAR_NO_EXCEPTIONS)
 
+#include "rar.hpp"
 
 void ErrorHandler::Clean()
 {
@@ -320,7 +321,11 @@ void ErrorHandler::Throw(RAR_EXIT Code)
     mprintf(L"\n%s\n",St(MProgAborted));
 #endif
   SetErrorCode(Code);
+#if defined(UNRAR_NO_EXCEPTIONS)
+  CHECK(false) << "Failed with RAR_EXIT code: " << Code;
+#else
   throw Code;
+#endif  // defined(UNRAR_NO_EXCEPTIONS)
 }
 
 
diff --git a/third_party/unrar/src/errhnd.hpp b/third_party/unrar/src/errhnd.hpp
index 26df96d5b436..1bcae41e7007 100644
--- a/third_party/unrar/src/errhnd.hpp
+++ b/third_party/unrar/src/errhnd.hpp
@@ -21,13 +21,12 @@ enum RAR_EXIT // RAR exit code.
 class ErrorHandler
 {
   private:
-    RAR_EXIT ExitCode;
-    uint ErrCount;
-    bool EnableBreak;
-    bool Silent;
-    bool DisableShutdown; // Shutdown is not suitable after last error.
+    RAR_EXIT ExitCode = RARX_SUCCESS;
+    uint ErrCount = 0;
+    bool EnableBreak = true;
+    bool Silent = false;
+    bool DisableShutdown = false; // Shutdown is not suitable after last error.
   public:
-    ErrorHandler();
     void Clean();
     void MemoryError();
     void OpenError(const wchar *FileName);
@@ -62,8 +61,8 @@ class ErrorHandler
     void SetSystemErrorCode(int Code);
     bool IsShutdownEnabled() {return !DisableShutdown;}
 
-    bool UserBreak; // Ctrl+Break is pressed.
-    bool MainExit; // main() is completed.
+    bool UserBreak = false; // Ctrl+Break is pressed.
+    bool MainExit = false; // main() is completed.
 };
 
 
diff --git a/third_party/unrar/src/file.cpp b/third_party/unrar/src/file.cpp
index 4ca83ad1ee6f..5188dbff715c 100644
--- a/third_party/unrar/src/file.cpp
+++ b/third_party/unrar/src/file.cpp
@@ -51,6 +51,11 @@ bool File::Open(const wchar *Name,uint Mode)
   bool UpdateMode=(Mode & FMF_UPDATE)!=0;
   bool WriteMode=(Mode & FMF_WRITE)!=0;
 #ifdef _WIN_ALL
+#if defined(CHROMIUM_UNRAR)
+  // Do not open a file handle since the sandbox doesn't allow it. Use the
+  // handle provided by the caller.
+  hNewFile = hOpenFile;
+#else
   uint Access=WriteMode ? GENERIC_WRITE:GENERIC_READ;
   if (UpdateMode)
     Access|=GENERIC_WRITE;
@@ -89,6 +94,14 @@ bool File::Open(const wchar *Name,uint Mode)
   if (hNewFile==FILE_BAD_HANDLE && LastError==ERROR_FILE_NOT_FOUND)
     ErrorType=FILE_NOTFOUND;
 
+#endif  // defined(CHROMIUM_UNRAR)
+
+#else
+
+#if defined(CHROMIUM_UNRAR)
+  // Do not open a file handle since the sandbox doesn't allow it. Use the
+  // handle provided by the caller.
+  int handle = hOpenFile;
 #else
   int flags=UpdateMode ? O_RDWR:(WriteMode ? O_WRONLY:O_RDONLY);
 #ifdef O_BINARY
@@ -99,8 +112,9 @@ bool File::Open(const wchar *Name,uint Mode)
 #endif
   char NameA[NM];
   WideToChar(Name,NameA,ASIZE(NameA));
-
   int handle=open(NameA,flags);
+#endif  // defined(CHROMIUM_UNRAR)
+
 #ifdef LOCK_EX
 
 #ifdef _OSF_SOURCE
@@ -230,6 +244,8 @@ bool File::Close()
   {
     if (!SkipClose)
     {
+#if !defined(CHROMIUM_UNRAR)
+// unrar should not close the file handle since it wasn't opened by unrar.
 #ifdef _WIN_ALL
       // We use the standard system handle for stdout in Windows
       // and it must not  be closed here.
@@ -242,6 +258,7 @@ bool File::Close()
       Success=fclose(hFile)!=EOF;
 #endif
 #endif
+#endif  // defined(CHROMIUM_UNRAR)
     }
     hFile=FILE_BAD_HANDLE;
   }
@@ -735,3 +752,9 @@ int64 File::Copy(File &Dest,int64 Length)
   return CopySize;
 }
 #endif
+
+#if defined(CHROMIUM_UNRAR)
+void File::SetFileHandle(FileHandle hF) {
+  hOpenFile = hF;
+}
+#endif  // defined(CHROMIUM_UNRAR)
diff --git a/third_party/unrar/src/file.hpp b/third_party/unrar/src/file.hpp
index 20734e28f62d..dd5cfecfbee9 100644
--- a/third_party/unrar/src/file.hpp
+++ b/third_party/unrar/src/file.hpp
@@ -68,6 +68,10 @@ class File
     wchar FileName[NM];
 
     FILE_ERRORTYPE ErrorType;
+
+#if defined(CHROMIUM_UNRAR)
+    FileHandle hOpenFile;
+#endif  // defined(CHROMIUM_UNRAR)
   public:
     File();
     virtual ~File();
@@ -111,6 +115,14 @@ class File
 #ifdef _WIN_ALL
     void RemoveSequentialFlag() {NoSequentialRead=true;}
 #endif
+
+#if defined(CHROMIUM_UNRAR)
+    // Since unrar runs in a sandbox, it doesn't have the permission to open
+    // files on the filesystem. Instead, the caller opens the file and passes
+    // the file handle to unrar. This handle is then used to read the file.
+    void SetFileHandle(FileHandle file);
+#endif  // defined(CHROMIUM_UNRAR)
+
 #ifdef _UNIX
     int GetFD()
     {
diff --git a/third_party/unrar/src/isnt.cpp b/third_party/unrar/src/isnt.cpp
index 6fadec049fe4..d30adf550925 100644
--- a/third_party/unrar/src/isnt.cpp
+++ b/third_party/unrar/src/isnt.cpp
@@ -1,24 +1,18 @@
 #include "rar.hpp"
 
 #ifdef _WIN_ALL
+#include "versionhelpers.h"
+
 DWORD WinNT()
 {
-  static int dwPlatformId=-1;
-  static DWORD dwMajorVersion,dwMinorVersion;
-  if (dwPlatformId==-1)
-  {
-    OSVERSIONINFO WinVer;
-    WinVer.dwOSVersionInfoSize=sizeof(WinVer);
-    GetVersionEx(&WinVer);
-    dwPlatformId=WinVer.dwPlatformId;
-    dwMajorVersion=WinVer.dwMajorVersion;
-    dwMinorVersion=WinVer.dwMinorVersion;
-  }
-  DWORD Result=0;
-  if (dwPlatformId==VER_PLATFORM_WIN32_NT)
-    Result=dwMajorVersion*0x100+dwMinorVersion;
-
-
-  return Result;
+  if (!IsWindowsXPOrGreater())
+    return WNT_NONE;
+  if (!IsWindowsVistaOrGreater())
+    return WNT_WXP;
+  if (!IsWindows7OrGreater()) return WNT_VISTA;
+  if (!IsWindows8OrGreater()) return WNT_W7;
+  if (!IsWindows8Point1OrGreater()) return WNT_W8;
+  if (!IsWindows10OrGreater()) return WNT_W81;
+  return WNT_W10;
 }
 #endif
diff --git a/third_party/unrar/src/isnt.hpp b/third_party/unrar/src/isnt.hpp
index 877d8801257a..a02174447e29 100644
--- a/third_party/unrar/src/isnt.hpp
+++ b/third_party/unrar/src/isnt.hpp
@@ -1,6 +1,8 @@
 #ifndef _RAR_ISNT_
 #define _RAR_ISNT_
 
+#include "windows.h"
+
 enum WINNT_VERSION {
   WNT_NONE=0,WNT_NT351=0x0333,WNT_NT4=0x0400,WNT_W2000=0x0500,
   WNT_WXP=0x0501,WNT_W2003=0x0502,WNT_VISTA=0x0600,WNT_W7=0x0601,
diff --git a/third_party/unrar/src/model.cpp b/third_party/unrar/src/model.cpp
index e91b44070e35..6c5c44384ccf 100644
--- a/third_party/unrar/src/model.cpp
+++ b/third_party/unrar/src/model.cpp
@@ -43,13 +43,27 @@ void ModelPPM::RestartModelRare()
   InitRL=-(MaxOrder < 12 ? MaxOrder:12)-1;
   MinContext = MaxContext = (RARPPM_CONTEXT*) SubAlloc.AllocContext();
   if (MinContext == NULL)
+  {
+#if defined(UNRAR_NO_EXCEPTIONS)
+    base::TerminateBecauseOutOfMemory(0);
+#else
     throw std::bad_alloc();
+#endif  // defined(UNRAR_NO_EXCEPTIONS)
+  }
+
   MinContext->Suffix=NULL;
   OrderFall=MaxOrder;
   MinContext->U.SummFreq=(MinContext->NumStats=256)+1;
   FoundState=MinContext->U.Stats=(RARPPM_STATE*)SubAlloc.AllocUnits(256/2);
   if (FoundState == NULL)
+  {
+#if defined(UNRAR_NO_EXCEPTIONS)
+    base::TerminateBecauseOutOfMemory(0);
+#else
     throw std::bad_alloc();
+#endif  // defined(UNRAR_NO_EXCEPTIONS)
+  }
+
   for (RunLength=InitRL, PrevSuccess=i=0;i < 256;i++) 
   {
     MinContext->U.Stats[i].Symbol=i;      
diff --git a/third_party/unrar/src/os.hpp b/third_party/unrar/src/os.hpp
index f235f625aef8..19bd6703d8d2 100644
--- a/third_party/unrar/src/os.hpp
+++ b/third_party/unrar/src/os.hpp
@@ -22,18 +22,25 @@
 
 #ifdef _WIN_ALL
 
-#define STRICT
+#ifndef STRICT
+#define STRICT 1
+#endif
+
+#if !defined(CHROMIUM_UNRAR)
 #define UNICODE
 #undef WINVER
 #undef _WIN32_WINNT
 #define WINVER 0x0501
 #define _WIN32_WINNT 0x0501
+#endif  // CHROMIUM_UNRAR
 
-#if !defined(ZIPSFX)
+#if !defined(ZIPSFX) && !defined(CHROMIUM_UNRAR)
 #define RAR_SMP
 #endif
 
+#if !defined(CHROMIUM_UNRAR)
 #define WIN32_LEAN_AND_MEAN
+#endif  // CHROMIUM_UNRAR
 
 #include <windows.h>
 #include <prsht.h>
@@ -65,8 +72,11 @@
   #include <direct.h>
   #include <intrin.h>
 
+#if !defined(CHROMIUM_UNRAR)
   #define USE_SSE
   #define SSE_ALIGNMENT 16
+#endif  // CHROMIUM_UNRAR
+
 #else
   #include <dirent.h>
 #endif // _MSC_VER
diff --git a/third_party/unrar/src/threadmisc.cpp b/third_party/unrar/src/threadmisc.cpp
index 4ad5af2e5681..9dfd2b9bc301 100644
--- a/third_party/unrar/src/threadmisc.cpp
+++ b/third_party/unrar/src/threadmisc.cpp
@@ -43,17 +43,22 @@ static inline void CriticalSectionEnd(CRITSECT_HANDLE *CritSection)
 }
 
 
-static struct GlobalPoolCreateSync
+struct GlobalPoolCreateSync
 {
   CRITSECT_HANDLE CritSection;
   GlobalPoolCreateSync()  { CriticalSectionCreate(&CritSection); }
   ~GlobalPoolCreateSync() { CriticalSectionDelete(&CritSection); }
-} PoolCreateSync;
+};
+
+static GlobalPoolCreateSync& GetPoolCreateSync() {
+  static GlobalPoolCreateSync PoolCreateSync;
+  return PoolCreateSync;
+}
 
 
 ThreadPool* CreateThreadPool()
 {
-  CriticalSectionStart(&PoolCreateSync.CritSection); 
+  CriticalSectionStart(&(GetPoolCreateSync().CritSection));
 
   if (GlobalPoolUseCount++ == 0)
     GlobalPool=new ThreadPool(MaxPoolThreads);
@@ -66,11 +71,11 @@ ThreadPool* CreateThreadPool()
   if (GlobalPoolUseCount > 1)
   {
     ThreadPool *Pool = new ThreadPool(MaxPoolThreads);
-    CriticalSectionEnd(&PoolCreateSync.CritSection); 
+    CriticalSectionEnd(&(GetPoolCreateSync().CritSection));
     return Pool;
   }
 
-  CriticalSectionEnd(&PoolCreateSync.CritSection); 
+  CriticalSectionEnd(&(GetPoolCreateSync().CritSection));
   return GlobalPool;
 }
 
@@ -79,7 +84,7 @@ void DestroyThreadPool(ThreadPool *Pool)
 {
   if (Pool!=NULL)
   {
-    CriticalSectionStart(&PoolCreateSync.CritSection); 
+    CriticalSectionStart(&(GetPoolCreateSync().CritSection));
 
     if (Pool==GlobalPool && GlobalPoolUseCount > 0 && --GlobalPoolUseCount == 0)
       delete GlobalPool;
@@ -89,7 +94,7 @@ void DestroyThreadPool(ThreadPool *Pool)
     if (Pool!=GlobalPool)
       delete Pool;
 
-    CriticalSectionEnd(&PoolCreateSync.CritSection); 
+    CriticalSectionEnd(&(GetPoolCreateSync().CritSection));
   }
 }
 
diff --git a/third_party/unrar/src/unicode.cpp b/third_party/unrar/src/unicode.cpp
index 8d01e73eb1a0..858f68e4a09b 100644
--- a/third_party/unrar/src/unicode.cpp
+++ b/third_party/unrar/src/unicode.cpp
@@ -1,7 +1,7 @@
 #include "rar.hpp"
 #define MBFUNCTIONS
 
-#if defined(_UNIX) && defined(MBFUNCTIONS)
+#if !defined(_WIN_ALL) && !defined(_APPLE) && defined(_UNIX) && defined(MBFUNCTIONS)
 
 static bool WideToCharMap(const wchar *Src,char *Dest,size_t DestSize,bool &Success);
 static void CharToWideMap(const char *Src,wchar *Dest,size_t DestSize,bool &Success);
@@ -30,7 +30,7 @@ bool WideToChar(const wchar *Src,char *Dest,size_t DestSize)
 #elif defined(_APPLE)
   WideToUtf(Src,Dest,DestSize);
 
-#elif defined(MBFUNCTIONS)
+#elif defined(_UNIX) && defined(MBFUNCTIONS)
   if (!WideToCharMap(Src,Dest,DestSize,RetCode))
   {
     mbstate_t ps; // Use thread safe external state based functions.
@@ -95,7 +95,7 @@ bool CharToWide(const char *Src,wchar *Dest,size_t DestSize)
 #elif defined(_APPLE)
   UtfToWide(Src,Dest,DestSize);
 
-#elif defined(MBFUNCTIONS)
+#elif defined(_UNIX) && defined(MBFUNCTIONS)
   mbstate_t ps;
   memset (&ps, 0, sizeof(ps));
   const char *SrcParam=Src; // mbsrtowcs can change the pointer.
@@ -128,7 +128,7 @@ bool CharToWide(const char *Src,wchar *Dest,size_t DestSize)
 }
 
 
-#if defined(_UNIX) && defined(MBFUNCTIONS)
+#if !defined(_WIN_ALL) && !defined(_APPLE) && defined(_UNIX) && defined(MBFUNCTIONS)
 // Convert and restore mapped inconvertible Unicode characters.
 // We use it for extended ASCII names in Unix.
 bool WideToCharMap(const wchar *Src,char *Dest,size_t DestSize,bool &Success)
@@ -172,7 +172,7 @@ bool WideToCharMap(const wchar *Src,char *Dest,size_t DestSize,bool &Success)
 #endif
 
 
-#if defined(_UNIX) && defined(MBFUNCTIONS)
+#if !defined(_WIN_ALL) && !defined(_APPLE) && defined(_UNIX) && defined(MBFUNCTIONS)
 // Convert and map inconvertible Unicode characters.
 // We use it for extended ASCII names in Unix.
 void CharToWideMap(const char *Src,wchar *Dest,size_t DestSize,bool &Success)
diff --git a/third_party/unrar/src/unpack.cpp b/third_party/unrar/src/unpack.cpp
index 1cda19c44501..ca3c52ea792b 100644
--- a/third_party/unrar/src/unpack.cpp
+++ b/third_party/unrar/src/unpack.cpp
@@ -1,3 +1,9 @@
+// NOTE(vakh): The process.h file needs to be included first because "rar.hpp"
+// defines certain macros that cause symbol redefinition errors
+#if defined(UNRAR_NO_EXCEPTIONS)
+#include "base/process/memory.h"
+#endif  // defined(UNRAR_NO_EXCEPTIONS)
+
 #include "rar.hpp"
 
 #include "coder.cpp"
@@ -89,7 +95,13 @@ void Unpack::Init(size_t WinSize,bool Solid)
 
   // We do not handle growth for existing fragmented window.
   if (Grow && Fragmented)
+  {
+#if defined(UNRAR_NO_EXCEPTIONS)
+    base::TerminateBecauseOutOfMemory(0);
+#else
     throw std::bad_alloc();
+#endif  // defined(UNRAR_NO_EXCEPTIONS)
+  }
 
   byte *NewWindow=Fragmented ? NULL : (byte *)malloc(WinSize);
 
@@ -99,7 +111,11 @@ void Unpack::Init(size_t WinSize,bool Solid)
     {
       // We do not support growth for new fragmented window.
       // Also exclude RAR4 and small dictionaries.
+#if defined(UNRAR_NO_EXCEPTIONS)
+      base::TerminateBecauseOutOfMemory(WinSize);
+#else
       throw std::bad_alloc();
+#endif  // defined(UNRAR_NO_EXCEPTIONS)
     }
     else
     {
diff --git a/third_party/unrar/src/unpack50frag.cpp b/third_party/unrar/src/unpack50frag.cpp
index 3c008ff24539..16d5b1c3d5ef 100644
--- a/third_party/unrar/src/unpack50frag.cpp
+++ b/third_party/unrar/src/unpack50frag.cpp
@@ -46,8 +46,14 @@ void FragmentedWindow::Init(size_t WinSize)
         break;
       Size-=Size/32;
     }
-    if (NewMem==NULL)
+    if (NewMem == NULL)
+    {
+#if defined(UNRAR_NO_EXCEPTIONS)
+      base::TerminateBecauseOutOfMemory(Size);
+#else
       throw std::bad_alloc();
+#endif  // defined(UNRAR_NO_EXCEPTIONS)
+    }
 
     // Clean the window to generate the same output when unpacking corrupt
     // RAR files, which may access to unused areas of sliding dictionary.
@@ -58,8 +64,14 @@ void FragmentedWindow::Init(size_t WinSize)
     MemSize[BlockNum]=TotalSize;
     BlockNum++;
   }
-  if (TotalSize<WinSize) // Not found enough free blocks.
+  if (TotalSize < WinSize)  // Not found enough free blocks.
+  {
+#if defined(UNRAR_NO_EXCEPTIONS)
+    base::TerminateBecauseOutOfMemory(WinSize);
+#else
     throw std::bad_alloc();
+#endif  // defined(UNRAR_NO_EXCEPTIONS)
+  }
 }
 
 
diff --git a/third_party/unrar/src/unrar_wrapper.h b/third_party/unrar/src/unrar_wrapper.h
new file mode 100644
index 000000000000..b19759da6f6e
--- /dev/null
+++ b/third_party/unrar/src/unrar_wrapper.h
@@ -0,0 +1,15 @@
+// Copyright 2018 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef THIRD_PARTY_UNRAR_SRC_UNRAR_WRAPPER_H_
+#define THIRD_PARTY_UNRAR_SRC_UNRAR_WRAPPER_H_
+
+#include "rar.hpp"
+
+namespace third_party_unrar {
+using ::Archive;
+static const int kUnrarEndarcHead = ::HEAD_ENDARC;
+}  // namespace third_party_unrar
+
+#endif  // THIRD_PARTY_UNRAR_SRC_UNRAR_WRAPPER_H_