cc: Move TextureMailbox::ReleaseCallback to SingleReleaseCallback.

cc/trees/layer_tree_host_pixeltest_readback.cc

Index: cc/trees/layer_tree_host_pixeltest_readback.cc
diff --git a/cc/trees/layer_tree_host_pixeltest_readback.cc b/cc/trees/layer_tree_host_pixeltest_readback.cc
index 1c8380b258db845d426d80a2c50054a13b9a49aa..aeb7ec27d106e1dfe7faf1717ec4a4b36c0fe5c6 100644
--- a/cc/trees/layer_tree_host_pixeltest_readback.cc
+++ b/cc/trees/layer_tree_host_pixeltest_readback.cc
@@ -58,13 +58,15 @@ class LayerTreeHostReadbackPixelTest : public LayerTreePixelTest {
     EXPECT_TRUE(proxy()->IsMainThread());
     EXPECT_TRUE(result->HasTexture());
 
-    scoped_ptr<TextureMailbox> texture_mailbox = result->TakeTexture().Pass();
-    EXPECT_TRUE(texture_mailbox->IsValid());
-    EXPECT_TRUE(texture_mailbox->IsTexture());
+    TextureMailbox texture_mailbox;
+    scoped_ptr<ScopedReleaseCallback> release_callback;
+    result->TakeTexture(&texture_mailbox, &release_callback);
+    EXPECT_TRUE(texture_mailbox.IsValid());
+    EXPECT_TRUE(texture_mailbox.IsTexture());
 
     scoped_ptr<SkBitmap> bitmap =
-        CopyTextureMailboxToBitmap(result->size(), *texture_mailbox);
-    texture_mailbox->RunReleaseCallback(0, false);
+        CopyTextureMailboxToBitmap(result->size(), texture_mailbox);
+    release_callback->Run(0, false);
 
     ReadbackResultAsBitmap(CopyOutputResult::CreateBitmapResult(bitmap.Pass()));
   }