BitmapContentLayerUpdater shouldn't reallocate bitmap smaller.

cc/resources/content_layer_updater.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/resources/content_layer_updater.h"
 
 #include "base/debug/trace_event.h"
 #include "base/time/time.h"
 #include "cc/debug/rendering_stats_instrumentation.h"
 #include "cc/resources/layer_painter.h"
@@ skipping 17 matching lines @@
       layer_is_opaque_(false) {}
 
 ContentLayerUpdater::~ContentLayerUpdater() {}
 
 void ContentLayerUpdater::set_rendering_stats_instrumentation(
     RenderingStatsInstrumentation* rsi) {
   rendering_stats_instrumentation_ = rsi;
 }
 
 void ContentLayerUpdater::PaintContents(SkCanvas* canvas,
-                                        gfx::Point origin,
+                                        gfx::Rect content_rect,
                                         float contents_width_scale,
                                         float contents_height_scale,
                                         gfx::Rect* resulting_opaque_rect) {
-  TRACE_EVENT0("cc", "ContentLayerUpdater::PaintContents");
+  TRACE_EVENT2("cc",
+               "ContentLayerUpdater::PaintContents",
+               "width",
+               content_rect.width(),
+               "height",
+               content_rect.height());
+  gfx::Point origin = content_rect.origin();
   canvas->save();
   canvas->translate(SkFloatToScalar(-origin.x()),
                     SkFloatToScalar(-origin.y()));
 
-  SkBaseDevice* device = canvas->getDevice();
-  gfx::Rect content_rect(origin, gfx::Size(device->width(), device->height()));
-
   gfx::Rect layer_rect = content_rect;
-
   if (contents_width_scale != 1.f || contents_height_scale != 1.f) {
     canvas->scale(SkFloatToScalar(contents_width_scale),
                   SkFloatToScalar(contents_height_scale));
 
     layer_rect = gfx::ScaleToEnclosingRect(
         content_rect, 1.f / contents_width_scale, 1.f / contents_height_scale);
   }
 
   SkRect layer_sk_rect = SkRect::MakeXYWH(
       layer_rect.x(), layer_rect.y(), layer_rect.width(), layer_rect.height());
@@ skipping 14 matching lines @@
   *resulting_opaque_rect = opaque_content_rect;
 
   content_rect_ = content_rect;
 }
 
 void ContentLayerUpdater::SetOpaque(bool opaque) {
   layer_is_opaque_ = opaque;
 }
 
 }  // namespace cc