flags: remove windows10-custom-titlebar

No longer needed per email discussion. Functionality retained behind
--enable-features=Windows10CustomTitlebar.

Bug: None
Change-Id: I2ba5afc63f89a5052611c116ae087dd7f1ca2743
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1499954
Commit-Queue: Elly Fong-Jones <ellyjones@chromium.org>
Commit-Queue: Bret Sepulveda <bsep@chromium.org>
Auto-Submit: Elly Fong-Jones <ellyjones@chromium.org>
Reviewed-by: Bret Sepulveda <bsep@chromium.org>
Cr-Commit-Position: refs/heads/master@{#637369}
diff --git a/chrome/browser/about_flags.cc b/chrome/browser/about_flags.cc
index 3011e2b5..142b9f3 100644
--- a/chrome/browser/about_flags.cc
+++ b/chrome/browser/about_flags.cc
@@ -2616,13 +2616,6 @@
      FEATURE_VALUE_TYPE(
          autofill::features::kAutofillSendExperimentIdsInPaymentsRPCs)},
 
-#if defined(OS_WIN)
-    {"windows10-custom-titlebar",
-     flag_descriptions::kWindows10CustomTitlebarName,
-     flag_descriptions::kWindows10CustomTitlebarDescription, kOsWin,
-     FEATURE_VALUE_TYPE(kWindows10CustomTitlebar)},
-#endif  // OS_WIN
-
 #if defined(OS_ANDROID)
     {"enable-autofill-manual-fallback",
      flag_descriptions::kAutofillManualFallbackAndroidName,
diff --git a/chrome/browser/flag-metadata.json b/chrome/browser/flag-metadata.json
index 806075b3..ce099a7a 100644
--- a/chrome/browser/flag-metadata.json
+++ b/chrome/browser/flag-metadata.json
@@ -3180,11 +3180,6 @@
     "expiry_milestone": 76
   },
   {
-    "name": "windows10-custom-titlebar",
-    // "owners": [ "your-team" ],
-    "expiry_milestone": 76
-  },
-  {
     "name": "windows-mixed-reality",
     "owners": [ "//device/vr/OWNERS", "xr-dev@chromium.org" ],
     "expiry_milestone": 76
diff --git a/chrome/browser/flag_descriptions.cc b/chrome/browser/flag_descriptions.cc
index dbdbd28..1e12004 100644
--- a/chrome/browser/flag_descriptions.cc
+++ b/chrome/browser/flag_descriptions.cc
@@ -2896,11 +2896,6 @@
     "Use Windows Runtime MIDI API for WebMIDI (effective only on Windows 10 or "
     "later).";
 
-const char kWindows10CustomTitlebarName[] = "Custom-drawn Windows 10 Titlebar";
-const char kWindows10CustomTitlebarDescription[] =
-    "If enabled, Chrome will draw the titlebar and caption buttons instead of "
-    "deferring to Windows.";
-
 #endif  // defined(OS_WIN)
 
 // Mac -------------------------------------------------------------------------
diff --git a/chrome/browser/flag_descriptions.h b/chrome/browser/flag_descriptions.h
index c41cc17c..143bfa4 100644
--- a/chrome/browser/flag_descriptions.h
+++ b/chrome/browser/flag_descriptions.h
@@ -1705,9 +1705,6 @@
 extern const char kUseWinrtMidiApiName[];
 extern const char kUseWinrtMidiApiDescription[];
 
-extern const char kWindows10CustomTitlebarName[];
-extern const char kWindows10CustomTitlebarDescription[];
-
 #endif  // defined(OS_WIN)
 
 // Mac ------------------------------------------------------------------------