Use MSAA in GPU rasterization if Skia suggests it

cc/base/switches.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 "cc/base/switches.h"
 
+#include <string>
+
 #include "base/command_line.h"
 
 namespace cc {
 namespace switches {
 
 // On platforms where checkerboards are used, prefer background colors instead
 // of checkerboards.
 const char kBackgroundColorInsteadOfCheckerboard[] =
     "background-color-instead-of-checkerboard";
 
@@ skipping 13 matching lines @@
 // Enables LCD text.
 const char kEnableLCDText[] = "enable-lcd-text";
 
 // Paint content on the compositor thread instead of the main thread.
 const char kEnableImplSidePainting[] = "enable-impl-side-painting";
 
 const char kEnableTopControlsPositionCalculation[] =
     "enable-top-controls-position-calculation";
 
 // Allow heuristics to determine when a layer tile should be drawn with
-// the Skia GPU backend.  Only valid with GPU accelerated compositing +
-// impl-side painting.
+// a Skia GPU backend. The backend can be selected explicitly by
+// appending "={gpu,msaa4,msaa16}".
+// Only valid with GPU accelerated compositing + impl-side painting.
 const char kEnableGPURasterization[] = "enable-gpu-rasterization";
 
 // Disable GPU rasterization, i.e. rasterize on the CPU only.
 // Overrides the kEnableGPURasterization flag.
 const char kDisableGPURasterization[] = "disable-gpu-rasterization";
 
 // The height of the movable top controls.
 const char kTopControlsHeight[] = "top-controls-height";
 
 // Percentage of the top controls need to be hidden before they will auto hide.
@@ skipping 117 matching lines @@
   const CommandLine& command_line = *CommandLine::ForCurrentProcess();
 
   if (command_line.HasSwitch(switches::kDisableGPURasterization))
     return false;
   else if (command_line.HasSwitch(switches::kEnableGPURasterization))
     return true;
 
   return false;
 }
 
+GpuRasterizationType GetGpuRasterizationType() {
+  const CommandLine& command_line = *CommandLine::ForCurrentProcess();
+
+  std::string type =
+      command_line.GetSwitchValueASCII(switches::kEnableGPURasterization);
+  if (type == "msaa4")
+    return GpuRasterizationMsaa4;
+  else if (type == "msaa16")
+    return GpuRasterizationMsaa4;
+
+  return GpuRasterizationGpu;
+}
+
 bool IsImplSidePaintingEnabled() {
   const CommandLine& command_line = *CommandLine::ForCurrentProcess();
 
   if (command_line.HasSwitch(switches::kDisableImplSidePainting))
     return false;
   else if (command_line.HasSwitch(switches::kEnableImplSidePainting))
     return true;
 
 #if defined(OS_ANDROID)
   return true;
 #else
   return false;
 #endif
 }
 
 bool IsMapImageEnabled() {
   const CommandLine& command_line = *CommandLine::ForCurrentProcess();
 
   if (command_line.HasSwitch(switches::kDisableMapImage))
     return false;
   else if (command_line.HasSwitch(switches::kEnableMapImage))
     return true;
 
   return false;
 }
 
 }  // namespace switches
 }  // namespace cc