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 ae8b74f46afd6a0ff047fae96b19a0721b904488..95f435d6816c94f84286993fa0268114368f5f82 100644
--- a/content/renderer/render_thread_impl.cc
+++ b/content/renderer/render_thread_impl.cc
@@ -586,6 +586,18 @@ 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_);

[danakj, 2015/01/26 21:04:32]

git cl format

[Stephen White, 2015/01/26 22:39:51]

Done.

+      DCHECK(parsed_msaa_sample_count) << string_value;
+      DCHECK_GT(gpu_rasterization_msaa_sample_count_, 0);
+      DCHECK_LE(gpu_rasterization_msaa_sample_count_, 16);

[danakj, 2015/01/26 21:04:32]

magic number duplication, i'd maybe not do this

[Stephen White, 2015/01/26 22:39:51]

Good idea. In fact, there's no reason for an upper max at all; Skia will just
ignore it if it's wacky. Removed everywhere.

+  } 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 +1354,10 @@ bool RenderThreadImpl::IsGpuRasterizationEnabled() {
   return is_gpu_rasterization_enabled_;
 }
 
+int RenderThreadImpl::GpuRasterizationMSAASampleCount() {
+  return gpu_rasterization_msaa_sample_count_;
+}
+
 bool RenderThreadImpl::IsLcdTextEnabled() {
   return is_lcd_text_enabled_;
 }