Back out r58711. It appears to have caused video/media-related ui_tests...

chrome/browser/renderer_host/browser_render_process_host.cc

Index: chrome/browser/renderer_host/browser_render_process_host.cc
===================================================================
--- chrome/browser/renderer_host/browser_render_process_host.cc	(revision 58729)
+++ chrome/browser/renderer_host/browser_render_process_host.cc	(working copy)
@@ -560,10 +560,10 @@
     // WebGLArray constructors on the DOMWindow visible. This
     // information is needed very early during bringup. We prefer to
     // use the WebPreferences to set this flag on a page-by-page basis.
-    switches::kDisableExperimentalWebGL,
+    switches::kEnableExperimentalWebGL,
     switches::kDisableGLSLTranslator,
     switches::kInProcessWebGL,
-    switches::kDisableAcceleratedCompositing,
+    switches::kEnableAcceleratedCompositing,
 #if defined(OS_MACOSX)
     // Allow this to be set when invoking the browser and relayed along.
     switches::kEnableSandboxLogging,
@@ -577,6 +577,7 @@
     switches::kDisableClickToPlay,
     switches::kEnableResourceContentSettings,
     switches::kPrelaunchGpuProcess,
+    switches::kEnableAcceleratedCompositing,
     switches::kEnableAcceleratedDecoding,
     switches::kEnableFileSystem,
   };