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

content/renderer/render_thread_impl.cc

Index: content/renderer/render_thread_impl.cc
diff --git a/content/renderer/render_thread_impl.cc b/content/renderer/render_thread_impl.cc
index ef6dae73a17d9089b2dd3944daba5ce839042c19..8b96121f06951b0c57556f4caf4b47384d7116b6 100644
--- a/content/renderer/render_thread_impl.cc
+++ b/content/renderer/render_thread_impl.cc
@@ -586,6 +586,17 @@ void RenderThreadImpl::Init() {
   is_gpu_rasterization_forced_ =
       command_line.HasSwitch(switches::kForceGpuRasterization);
 
+  if (command_line.HasSwitch(switches::kGpuRasterizationMSAASampleCount)) {
+    std::string string_value = command_line.GetSwitchValueASCII(
+        switches::kGpuRasterizationMSAASampleCount);
+    bool parsed_msaa_sample_count =
+        base::StringToInt(string_value, &gpu_rasterization_msaa_sample_count_);
+    DCHECK(parsed_msaa_sample_count) << string_value;
+    DCHECK_GE(gpu_rasterization_msaa_sample_count_, 0);
+  } else {
+    gpu_rasterization_msaa_sample_count_ = 0;
+  }
+
   if (command_line.HasSwitch(switches::kDisableDistanceFieldText)) {
     is_distance_field_text_enabled_ = false;
   } else if (command_line.HasSwitch(switches::kEnableDistanceFieldText)) {
@@ -1342,6 +1353,10 @@ bool RenderThreadImpl::IsGpuRasterizationEnabled() {
   return is_gpu_rasterization_enabled_;
 }
 
+int RenderThreadImpl::GetGpuRasterizationMSAASampleCount() {
+  return gpu_rasterization_msaa_sample_count_;
+}
+
 bool RenderThreadImpl::IsLcdTextEnabled() {
   return is_lcd_text_enabled_;
 }