Revert of Remove EnableThreadedCompositing from the browser.

chrome/browser/about_flags.cc

Index: chrome/browser/about_flags.cc
diff --git a/chrome/browser/about_flags.cc b/chrome/browser/about_flags.cc
index 3cf6d422950b00374dbc17dfc342fcd861254c46..7577556a0b3e3a97ca013d70cf3a88c938e8c25c 100644
--- a/chrome/browser/about_flags.cc
+++ b/chrome/browser/about_flags.cc
@@ -503,6 +503,18 @@
     SINGLE_VALUE_TYPE(switches::kIgnoreGpuBlacklist)
   },
   {
+    "threaded-compositing-mode",
+    IDS_FLAGS_THREADED_COMPOSITING_MODE_NAME,
+    IDS_FLAGS_THREADED_COMPOSITING_MODE_DESCRIPTION,
+#if !defined(USE_AURA)
+    kOsLinux,
+#else
+    0,
+#endif
+    ENABLE_DISABLE_VALUE_TYPE(switches::kEnableThreadedCompositing,
+                              switches::kDisableThreadedCompositing)
+  },
+  {
     "force-accelerated-composited-scrolling",
      IDS_FLAGS_FORCE_ACCELERATED_OVERFLOW_SCROLL_MODE_NAME,
      IDS_FLAGS_FORCE_ACCELERATED_OVERFLOW_SCROLL_MODE_DESCRIPTION,