Add a command-line flag to set GPU rasterization multisampling.

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 1063 matching lines @@
     command_line->AppendSwitchASCII(
         switches::kNumRasterThreads,
         base::IntToString(NumberOfRendererRasterThreads()));
   } else {
     command_line->AppendSwitch(switches::kDisableImplSidePainting);
   }
 
   if (IsGpuRasterizationEnabled())
     command_line->AppendSwitch(switches::kEnableGpuRasterization);
 
+  if (GpuRasterizationMSAASampleCount() > 0) {

[danakj, 2015/01/27 17:59:35]

FWIW You could remove the if() here and the if(HasSwitch) in the
RenderThreadImpl.

[piman, 2015/01/27 18:07:16]

nit: cache the return value of GpuRasterizationMSAASampleCount()? It parses
strings, and we use it twice.

[Stephen White, 2015/01/27 18:11:45]

Done.

+    command_line->AppendSwitchASCII(
+        switches::kGpuRasterizationMSAASampleCount,
+        base::IntToString(GpuRasterizationMSAASampleCount()));
+  }
+
   DCHECK_IMPLIES(IsZeroCopyUploadEnabled(), !IsOneCopyUploadEnabled());
   DCHECK_IMPLIES(IsOneCopyUploadEnabled(), !IsZeroCopyUploadEnabled());
   if (IsZeroCopyUploadEnabled())
     command_line->AppendSwitch(switches::kEnableZeroCopy);
   if (!IsOneCopyUploadEnabled())
     command_line->AppendSwitch(switches::kDisableOneCopy);
 
   if (IsForceGpuRasterizationEnabled())

[danakj, 2015/01/27 17:59:35]

Ah ya, I missed this, sorry. LGTM

     command_line->AppendSwitch(switches::kForceGpuRasterization);
 
   if (BrowserGpuChannelHostFactory::IsGpuMemoryBufferFactoryUsageEnabled(
           gfx::GpuMemoryBuffer::MAP)) {
     std::vector<gfx::GpuMemoryBufferType> supported_types;
     GpuMemoryBufferFactory::GetSupportedTypes(&supported_types);
     DCHECK(!supported_types.empty());
 
     // The GPU service will always use the preferred type.
     gfx::GpuMemoryBufferType type = supported_types[0];
@@ skipping 1268 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