BitmapContentLayerUpdater shouldn't reallocate bitmap smaller.

cc/resources/content_layer_updater.cc

Index: cc/resources/content_layer_updater.cc
diff --git a/cc/resources/content_layer_updater.cc b/cc/resources/content_layer_updater.cc
index 2e73c4bb904d587e9a3c9935ba827d0ba20ec0c9..92cabf2c66da9175da7cde477688eb4e353224e1 100644
--- a/cc/resources/content_layer_updater.cc
+++ b/cc/resources/content_layer_updater.cc
@@ -35,20 +35,22 @@ void ContentLayerUpdater::set_rendering_stats_instrumentation(
 }
 
 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));