gpu: Add async pixel transfer interface, stub and tests.

gpu/command_buffer/service/query_manager.cc

Index: gpu/command_buffer/service/query_manager.cc
diff --git a/gpu/command_buffer/service/query_manager.cc b/gpu/command_buffer/service/query_manager.cc
index 61a8d7f55c68794ff38eccdd011005c3cef5f54c..51055e2034a46fa5012ad2cc9c046903bfa24010 100644
--- a/gpu/command_buffer/service/query_manager.cc
+++ b/gpu/command_buffer/service/query_manager.cc
@@ -4,11 +4,13 @@
 
 #include "gpu/command_buffer/service/query_manager.h"
 #include "base/atomicops.h"
+#include "base/bind.h"
 #include "base/logging.h"
 #include "base/time.h"
 #include "gpu/command_buffer/common/gles2_cmd_format.h"
 #include "gpu/command_buffer/service/gles2_cmd_decoder.h"
 #include "gpu/command_buffer/service/feature_info.h"
+#include "ui/gl/async_pixel_transfer_delegate.h"
 
 namespace gpu {
 namespace gles2 {
@@ -162,7 +164,9 @@ void CommandLatencyQuery::Destroy(bool /* have_context */) {
 CommandLatencyQuery::~CommandLatencyQuery() {
 }
 
-class AsyncPixelTransfersCompletedQuery : public QueryManager::Query {
+class AsyncPixelTransfersCompletedQuery
+    : public QueryManager::Query
+    , public base::SupportsWeakPtr<AsyncPixelTransfersCompletedQuery> {
  public:
   AsyncPixelTransfersCompletedQuery(
       QueryManager* manager, GLenum target, int32 shm_id, uint32 shm_offset);
@@ -172,6 +176,8 @@ class AsyncPixelTransfersCompletedQuery : public QueryManager::Query {
   virtual bool Process() OVERRIDE;
   virtual void Destroy(bool have_context) OVERRIDE;
 
+  void MarkAsCompletedCallback() { MarkAsCompleted(1); }
+
  protected:
   virtual ~AsyncPixelTransfersCompletedQuery();
 };
@@ -186,12 +192,24 @@ bool AsyncPixelTransfersCompletedQuery::Begin() {
 }
 
 bool AsyncPixelTransfersCompletedQuery::End(uint32 submit_count) {
-  // TODO(epenner): Mark completion via an async task.
-  // TODO(epenner): This will be a boolean to start, indicating
-  // completion of all tasks in the query. We could change this
-  // to return a count of tasks completed instead.
   MarkAsPending(submit_count);
-  return MarkAsCompleted(1);
+
+  // This will call MarkAsCompleted(1) as a reply to a task on
+  // the async upload thread, such that it occurs after all previous
+  // async transfers have completed.
+  manager()->decoder()->GetAsyncPixelTransferDelegate()->AsyncNotifyCompletion(
+      base::Bind(
+          &AsyncPixelTransfersCompletedQuery::MarkAsCompletedCallback,
+          AsWeakPtr()));
+
+  // TODO(epenner): The async task occurs outside the normal
+  // flow, via a callback on this thread. Is there anything
+  // missing or wrong with that?
+
+  // TODO(epenner): Could we possibly trigger the completion on
+  // the upload thread by writing to the query shared memory
+  // directly?
+  return true;
 }
 
 bool AsyncPixelTransfersCompletedQuery::Process() {