cc, gpu: Use RGBA when using msaa on systems that don't support BGRA

cc/raster/gpu_tile_task_worker_pool.cc

 // Copyright 2014 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/raster/gpu_tile_task_worker_pool.h"
 
 #include <algorithm>
 
 #include "base/trace_event/trace_event.h"
 #include "cc/playback/raster_source.h"
@@ skipping 190 matching lines @@
 void GpuTileTaskWorkerPool::CheckForCompletedTasks() {
   TRACE_EVENT0("cc", "GpuTileTaskWorkerPool::CheckForCompletedTasks");
 
   task_graph_runner_->CollectCompletedTasks(namespace_token_,
                                             &completed_tasks_);
   CompleteTasks(completed_tasks_);
   completed_tasks_.clear();
 }
 
 ResourceFormat GpuTileTaskWorkerPool::GetResourceFormat() {
-  return rasterizer_->resource_provider()->best_texture_format();
+  ResourceFormat format =

[vmiura, 2015/06/09 23:05:11]

We call this per-tile.  I think it'd be good to pre-calc this and return via
something like ResourceProvider::best_renderbuffer_format().

+      rasterizer_->resource_provider()->best_texture_format();
+  if (rasterizer_->msaa_sample_count()) {
+    const ContextProvider::Capabilities& caps = rasterizer_->resource_provider()
+                                                    ->output_surface()
+                                                    ->context_provider()
+                                                    ->ContextCapabilities();
+    if (!caps.gpu.render_buffer_format_bgra8888)
+      return ResourceFormat::RGBA_8888;
+  }
+  return format;
 }
 
 void GpuTileTaskWorkerPool::CompleteTasks(const Task::Vector& tasks) {
   for (auto& task : tasks) {
     RasterTask* raster_task = static_cast<RasterTask*>(task.get());
 
     raster_task->WillComplete();
     raster_task->CompleteOnOriginThread(this);
     raster_task->DidComplete();
 
@@ skipping 18 matching lines @@
 void GpuTileTaskWorkerPool::OnTaskSetFinished(TaskSet task_set) {
   TRACE_EVENT1("cc", "GpuTileTaskWorkerPool::OnTaskSetFinished", "task_set",
                task_set);
 
   DCHECK(tasks_pending_[task_set]);
   tasks_pending_[task_set] = false;
   client_->DidFinishRunningTileTasks(task_set);
 }
 
 }  // namespace cc