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

gpu/command_buffer/service/texture_manager.h

Index: gpu/command_buffer/service/texture_manager.h
diff --git a/gpu/command_buffer/service/texture_manager.h b/gpu/command_buffer/service/texture_manager.h
index ed4c8c9ec02254113648115bbf9c9d5be8fa5cea..2c09cd4d6301f79a4366cd1b2abc0eb7381a860d 100644
--- a/gpu/command_buffer/service/texture_manager.h
+++ b/gpu/command_buffer/service/texture_manager.h
@@ -14,6 +14,7 @@
 #include "gpu/command_buffer/service/feature_info.h"
 #include "gpu/command_buffer/service/gl_utils.h"
 #include "gpu/gpu_export.h"
+#include "ui/gl/async_pixel_transfer_delegate.h"
 #include "ui/gl/gl_image.h"
 
 namespace gpu {
@@ -175,6 +176,15 @@ class GPU_EXPORT TextureManager {
       return stream_texture_;
     }
 
+    gfx::AsyncPixelTransferState* AsyncTransferState() {
+      DCHECK(service_id_ != 0);
+      if (!async_transfer_state_)
+          async_transfer_state_ =
+              gfx::AsyncPixelTransferDelegate::Get()->
+                  CreatePixelTransferState(service_id_);
+      return async_transfer_state_.get();
+    }
+
     void SetImmutable(bool immutable) {
       immutable_ = immutable;
     }
@@ -337,6 +347,9 @@ class GPU_EXPORT TextureManager {
     // Whether this is a special streaming texture.
     bool stream_texture_;
 
+    // State to facilitate async transfers on this texture.
+    scoped_refptr<gfx::AsyncPixelTransferState> async_transfer_state_;
+
     // Whether the texture is immutable and no further changes to the format
     // or dimensions of the texture object can be made.
     bool immutable_;