Revert "Remove impl-side-painting from about:flags"

content/renderer/render_thread_impl.cc

 // Copyright (c) 2012 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.
 
 #include "content/renderer/render_thread_impl.h"
 
 #include <algorithm>
 #include <limits>
 #include <map>
 #include <vector>
@@ skipping 505 matching lines @@
   AddFilter((new EmbeddedWorkerContextMessageFilter())->GetFilter());
 
   GetContentClient()->renderer()->RenderThreadStarted();
 
   InitSkiaEventTracer();
 
   const base::CommandLine& command_line =
       *base::CommandLine::ForCurrentProcess();
 
   is_impl_side_painting_enabled_ =
-      !command_line.HasSwitch(switches::kDisableImplSidePainting);
+      command_line.HasSwitch(switches::kEnableImplSidePainting);
   cc_blink::WebLayerImpl::SetImplSidePaintingEnabled(
       is_impl_side_painting_enabled_);
 
   is_zero_copy_enabled_ = command_line.HasSwitch(switches::kEnableZeroCopy);
 
 #if defined(OS_MACOSX) || defined(OS_ANDROID)
   // TODO(danakj): If changing these also update NumberOfRendererRasterThreads
   // in compositor_util.cc. We should be using methods from compositor_util here
   // instead of inspecting flags.
   is_one_copy_enabled_ = command_line.HasSwitch(switches::kEnableOneCopy);
@@ skipping 1232 matching lines @@
   hidden_widget_count_--;
 
   if (!GetContentClient()->renderer()->RunIdleHandlerWhenWidgetsHidden()) {
     return;
   }
 
   ScheduleIdleHandler(kLongIdleHandlerDelayMs);
 }
 
 }  // namespace content