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

content/browser/renderer_host/render_process_host_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.
 
 // Represents the browser side of the browser <--> renderer communication
 // channel. There will be one RenderProcessHost per renderer process.
 
 #include "content/browser/renderer_host/render_process_host_impl.h"
 
 #include <algorithm>
@@ skipping 1053 matching lines @@
 }
 
 static void AppendCompositorCommandLineFlags(base::CommandLine* command_line) {
   if (IsPinchVirtualViewportEnabled())
     command_line->AppendSwitch(cc::switches::kEnablePinchVirtualViewport);
 
   if (IsDelegatedRendererEnabled())
     command_line->AppendSwitch(switches::kEnableDelegatedRenderer);
 
   if (IsImplSidePaintingEnabled()) {
+    command_line->AppendSwitch(switches::kEnableImplSidePainting);
     command_line->AppendSwitchASCII(
         switches::kNumRasterThreads,
         base::IntToString(NumberOfRendererRasterThreads()));
-  } else {
-    command_line->AppendSwitch(switches::kDisableImplSidePainting);
   }
 
   if (IsGpuRasterizationEnabled())
     command_line->AppendSwitch(switches::kEnableGpuRasterization);
 
   DCHECK_IMPLIES(IsZeroCopyUploadEnabled(), !IsOneCopyUploadEnabled());
   DCHECK_IMPLIES(IsOneCopyUploadEnabled(), !IsZeroCopyUploadEnabled());
   if (IsZeroCopyUploadEnabled())
     command_line->AppendSwitch(switches::kEnableZeroCopy);
   if (!IsOneCopyUploadEnabled())
@@ skipping 1271 matching lines @@
 
 void RenderProcessHostImpl::DecrementWorkerRefCount() {
   DCHECK_CURRENTLY_ON(BrowserThread::UI);
   DCHECK_GT(worker_ref_count_, 0);
   --worker_ref_count_;
   if (worker_ref_count_ == 0)
     Cleanup();
 }
 
 }  // namespace content