huddly-updater: replace FALLTHROUGH by C++17 attribute [[fallthrough]]

The deprecated macro will be removed from libchrome r958576.

BUG=b:211560276
TEST=FEATURES=test emerge-endeavour huddly-updater

Change-Id: I0d0443f7ae09b1511f14b93e5643609256519ae2
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/huddly-updater/+/3571143
Tested-by: Grace Cham <hscham@chromium.org>
Reviewed-by: Kyle Williams <kdgwill@chromium.org>
Commit-Queue: Grace Cham <hscham@chromium.org>
diff --git a/src/common/messagepack/messagepack.cc b/src/common/messagepack/messagepack.cc
index a619c93..3b16b29 100644
--- a/src/common/messagepack/messagepack.cc
+++ b/src/common/messagepack/messagepack.cc
@@ -3,7 +3,6 @@
 // found in the LICENSE file.
 #include "messagepack.h"
 
-#include <base/compiler_specific.h>
 #include <base/logging.h>
 
 // Macro for telling -Wimplicit-fallthrough that a fallthrough is intentional.
@@ -149,21 +148,21 @@
       *out = object_.via.i64;
       return true;
     case MSGPACK_OBJECT_FLOAT32:
-      FALLTHROUGH;
+      [[fallthrough]];
     case MSGPACK_OBJECT_FLOAT:
-      FALLTHROUGH;
+      [[fallthrough]];
     case MSGPACK_OBJECT_BOOLEAN:
-      FALLTHROUGH;
+      [[fallthrough]];
     case MSGPACK_OBJECT_NIL:
-      FALLTHROUGH;
+      [[fallthrough]];
     case MSGPACK_OBJECT_STR:
-      FALLTHROUGH;
+      [[fallthrough]];
     case MSGPACK_OBJECT_ARRAY:
-      FALLTHROUGH;
+      [[fallthrough]];
     case MSGPACK_OBJECT_MAP:
-      FALLTHROUGH;
+      [[fallthrough]];
     case MSGPACK_OBJECT_BIN:
-      FALLTHROUGH;
+      [[fallthrough]];
     case MSGPACK_OBJECT_EXT:
       return false;
   }
@@ -179,21 +178,21 @@
       *out = static_cast<uint64_t>(object_.via.i64);
       return true;
     case MSGPACK_OBJECT_FLOAT32:
-      FALLTHROUGH;
+      [[fallthrough]];
     case MSGPACK_OBJECT_FLOAT:
-      FALLTHROUGH;
+      [[fallthrough]];
     case MSGPACK_OBJECT_BOOLEAN:
-      FALLTHROUGH;
+      [[fallthrough]];
     case MSGPACK_OBJECT_NIL:
-      FALLTHROUGH;
+      [[fallthrough]];
     case MSGPACK_OBJECT_STR:
-      FALLTHROUGH;
+      [[fallthrough]];
     case MSGPACK_OBJECT_ARRAY:
-      FALLTHROUGH;
+      [[fallthrough]];
     case MSGPACK_OBJECT_MAP:
-      FALLTHROUGH;
+      [[fallthrough]];
     case MSGPACK_OBJECT_BIN:
-      FALLTHROUGH;
+      [[fallthrough]];
     case MSGPACK_OBJECT_EXT:
       return false;
   }
@@ -209,22 +208,22 @@
       *out = static_cast<double>(object_.via.i64);
       return true;
     case MSGPACK_OBJECT_FLOAT32:
-      FALLTHROUGH;
+      [[fallthrough]];
     case MSGPACK_OBJECT_FLOAT:
       *out = object_.via.f64;
       return true;
     case MSGPACK_OBJECT_BOOLEAN:
-      FALLTHROUGH;
+      [[fallthrough]];
     case MSGPACK_OBJECT_NIL:
-      FALLTHROUGH;
+      [[fallthrough]];
     case MSGPACK_OBJECT_STR:
-      FALLTHROUGH;
+      [[fallthrough]];
     case MSGPACK_OBJECT_ARRAY:
-      FALLTHROUGH;
+      [[fallthrough]];
     case MSGPACK_OBJECT_MAP:
-      FALLTHROUGH;
+      [[fallthrough]];
     case MSGPACK_OBJECT_BIN:
-      FALLTHROUGH;
+      [[fallthrough]];
     case MSGPACK_OBJECT_EXT:
       return false;
   }