(not for commit) Simplified multi-threaded Ganesh with lock on Flush only.

cc/resources/gpu_tile_task_worker_pool.cc

Index: cc/resources/gpu_tile_task_worker_pool.cc
diff --git a/cc/resources/gpu_tile_task_worker_pool.cc b/cc/resources/gpu_tile_task_worker_pool.cc
index 824945740b97b0bbd049f8790c85e599733a58c3..f07f610fd8d51b73b3ab4c4b996401f370a28388 100644
--- a/cc/resources/gpu_tile_task_worker_pool.cc
+++ b/cc/resources/gpu_tile_task_worker_pool.cc
@@ -6,7 +6,9 @@
 
 #include <algorithm>
 
+#include "base/threading/platform_thread.h"
 #include "base/trace_event/trace_event.h"
+#include "cc/output/context_provider.h"
 #include "cc/resources/raster_buffer.h"
 #include "cc/resources/raster_source.h"
 #include "cc/resources/resource.h"
@@ -16,34 +18,93 @@
 #include "third_party/skia/include/core/SkPictureRecorder.h"
 #include "third_party/skia/include/core/SkSurface.h"
 #include "third_party/skia/include/gpu/GrContext.h"
+using gpu::gles2::GLES2Interface;
 
 namespace cc {
 namespace {
 
 class RasterBufferImpl : public RasterBuffer {
  public:
-  RasterBufferImpl() {}
+  RasterBufferImpl(ResourceProvider* resource_provider,
+                   const Resource* resource,
+                   bool use_distance_field_text)
+      : lock_(resource_provider, resource->id()),
+        resource_provider_(resource_provider),
+        resource_(resource),
+        sk_surface_(nullptr),
+        use_distance_field_text_(use_distance_field_text) {}
 
   // Overridden from RasterBuffer:
   void Playback(const RasterSource* raster_source,
                 const gfx::Rect& rect,
                 float scale) override {
-    // Don't do anything.
+    TRACE_EVENT0("cc", "RasterBufferImpl::Playback");
+
+    // Play back raster_source into temp SkPicture.
+    SkPictureRecorder recorder;
+    gfx::Size size = resource_->size();
+    const int flags = SkPictureRecorder::kComputeSaveLayerInfo_RecordFlag;
+    skia::RefPtr<SkCanvas> canvas = skia::SharePtr(
+        recorder.beginRecording(size.width(), size.height(), NULL, flags));
+
+    canvas->save();
+    raster_source->PlaybackToCanvas(canvas.get(), rect, scale);
+    canvas->restore();
+
+    skia::RefPtr<SkPicture> picture = skia::AdoptRef(recorder.endRecording());
+
+    // Bind ContextProvider to current thread.
+    resource_provider_->output_surface()
+        ->worker_context_provider()
+        ->RebindToCurrentThread();
+
+    // Draw picture to Resource's texture.
+    {
+      ScopedGpuRaster gpu_raster(
+          resource_provider_->output_surface()->worker_context_provider());
+
+      skia::RefPtr<SkSurface> sk_surface = skia::AdoptRef(
+          lock_.GetSkSurface(use_distance_field_text_, false, 0));
+
+#ifdef TODO_VMIURA_SINGLE_PICTURE_PLAYBACK
+      // This doesn't work if layer hoisting is enabled :(.
+      picture->playback(sk_surface->getCanvas(), nullptr);
+#else
+      // This works...
+      SkMultiPictureDraw multi_picture_draw;
+      multi_picture_draw.add(sk_surface->getCanvas(), picture.get());
+      multi_picture_draw.draw(false);
+#endif
+      sk_surface.clear();
+    }
+
+    // Save Flush point after this tile, which the cc thread executes
+    // via SafeFlush().
+    resource_provider_->output_surface()
+        ->worker_context_provider()
+        ->ContextGL()
+        ->SetSafeFlushPoint();
   }
 
  private:
+  ResourceProvider::ScopedWriteLockGr lock_;
+  ResourceProvider* resource_provider_;
+  const Resource* resource_;
+  SkSurface* sk_surface_;
+  bool use_distance_field_text_;
+
   DISALLOW_COPY_AND_ASSIGN(RasterBufferImpl);
 };
 
 }  // namespace
+
 // static
 scoped_ptr<TileTaskWorkerPool> GpuTileTaskWorkerPool::Create(
     base::SequencedTaskRunner* task_runner,
     TaskGraphRunner* task_graph_runner,
     ResourceProvider* resource_provider) {
-  return make_scoped_ptr<TileTaskWorkerPool>(
-      new GpuTileTaskWorkerPool(
-          task_runner, task_graph_runner, resource_provider));
+  return make_scoped_ptr<TileTaskWorkerPool>(new GpuTileTaskWorkerPool(
+      task_runner, task_graph_runner, resource_provider));
 }
 
 // TODO(hendrikw): This class should be removed.  See crbug.com/444938.
@@ -53,8 +114,8 @@ GpuTileTaskWorkerPool::GpuTileTaskWorkerPool(
     ResourceProvider* resource_provider)
     : task_runner_(task_runner),
       task_graph_runner_(task_graph_runner),
-      namespace_token_(task_graph_runner_->GetNamespaceToken()),
       resource_provider_(resource_provider),
+      namespace_token_(task_graph_runner_->GetNamespaceToken()),
       task_set_finished_weak_ptr_factory_(this),
       weak_ptr_factory_(this) {
 }
@@ -106,7 +167,8 @@ void GpuTileTaskWorkerPool::ScheduleTasks(TileTaskQueue* queue) {
   for (TileTaskQueue::Item::Vector::const_iterator it = queue->items.begin();
        it != queue->items.end(); ++it) {
     const TileTaskQueue::Item& item = *it;
-    RasterTask* task = item.task;
+    RasterTask* task = item.task->AsRasterTask();
+    DCHECK(task);
     DCHECK(!task->HasCompleted());
 
     for (TaskSet task_set = 0; task_set < kNumberOfTaskSets; ++task_set) {
@@ -129,6 +191,13 @@ void GpuTileTaskWorkerPool::ScheduleTasks(TileTaskQueue* queue) {
   }
 
   ScheduleTasksOnOriginThread(this, &graph_);
+
+  // Flush compositor context to sync resources to worker context.
+  resource_provider_->output_surface()
+      ->context_provider()
+      ->ContextGL()
+      ->ShallowFlushCHROMIUM();
+
   task_graph_runner_->ScheduleTasks(namespace_token_, &graph_);
 
   std::copy(new_task_set_finished_tasks,
@@ -141,6 +210,14 @@ void GpuTileTaskWorkerPool::CheckForCompletedTasks() {
 
   task_graph_runner_->CollectCompletedTasks(namespace_token_,
                                             &completed_tasks_);
+
+  // Flush worker context so raster outputs are synced to the compositor
+  // context.
+  resource_provider_->output_surface()
+      ->worker_context_provider()
+      ->ContextGL()
+      ->SafeFlush();
+
   CompleteTasks(completed_tasks_);
   completed_tasks_.clear();
 }
@@ -164,7 +241,9 @@ void GpuTileTaskWorkerPool::CompleteTasks(const Task::Vector& tasks) {
 
 scoped_ptr<RasterBuffer> GpuTileTaskWorkerPool::AcquireBufferForRaster(
     const Resource* resource) {
-  return make_scoped_ptr<RasterBuffer>(new RasterBufferImpl());
+  bool use_distance_field_text = false;
+  return make_scoped_ptr<RasterBuffer>(new RasterBufferImpl(
+      resource_provider_, resource, use_distance_field_text));
 }
 
 void GpuTileTaskWorkerPool::ReleaseBufferForRaster(