cc: Adding support for RGBA_4444 tile textures

cc/layers/tiled_layer.cc

 // Copyright 2011 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/layers/tiled_layer.h"
 
 #include <algorithm>
 #include <vector>
 
 #include "base/auto_reset.h"
@@ skipping 68 matching lines @@
         occluded(false),
         updater_resource_(updater_resource.Pass()) {}
 
   scoped_ptr<LayerUpdater::Resource> updater_resource_;
 
   DISALLOW_COPY_AND_ASSIGN(UpdatableTile);
 };
 
 TiledLayer::TiledLayer()
     : ContentsScalingLayer(),
-      texture_format_(GL_INVALID_ENUM),
+      texture_format_(RGBA_8888),
       skips_draw_(false),
       failed_update_(false),
       tiling_option_(AUTO_TILE) {
   tiler_ =
       LayerTilingData::Create(gfx::Size(), LayerTilingData::HAS_BORDER_TEXELS);
 }
 
 TiledLayer::~TiledLayer() {}
 
 scoped_ptr<LayerImpl> TiledLayer::CreateLayerImpl(LayerTreeImpl* tree_impl) {
@@ skipping 794 matching lines @@
   gfx::Rect prepaint_rect = visible_content_rect();
   prepaint_rect.Inset(-tiler_->tile_size().width() * kPrepaintColumns,
                       -tiler_->tile_size().height() * kPrepaintRows);
   gfx::Rect content_rect(content_bounds());
   prepaint_rect.Intersect(content_rect);
 
   return prepaint_rect;
 }
 
 }  // namespace cc