android: Don't cast to SurfaceLayer

It's not safe to assume a layer that draws in the content layer
hierarchy must be the SurfaceLayer. It could also be the touch handles.
Code doesn't need anything from SurfaceLayer anyway, so just don't cast
at all.

Change-Id: I4ea8aa9868cf24017e23820a8f303f56be1ba26e
Reviewed-on: https://chromium-review.googlesource.com/1074148
Reviewed-by: David Trainor <dtrainor@chromium.org>
Commit-Queue: Bo <boliu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#562075}

chrome/browser/android/compositor/layer/content_layer.cc

@@ -7,7 +7,6 @@
 #include "base/lazy_instance.h"
 #include "cc/layers/layer.h"
 #include "cc/layers/layer_collections.h"
-#include "cc/layers/surface_layer.h"
 #include "cc/paint/filter_operations.h"
 #include "chrome/browser/android/compositor/layer/thumbnail_layer.h"
 #include "chrome/browser/android/compositor/tab_content_manager.h"
@@ -113,10 +112,9 @@ gfx::Size ContentLayer::ComputeSize(int id) const {
   gfx::Size size;
 
   scoped_refptr<cc::Layer> live_layer = tab_content_manager_->GetLiveLayer(id);
-  cc::SurfaceLayer* surface_layer =
-      static_cast<cc::SurfaceLayer*>(GetDrawsContentLeaf(live_layer));
-  if (surface_layer)
-    size.SetToMax(surface_layer->bounds());
+  cc::Layer* leaf_that_draws = GetDrawsContentLeaf(live_layer);
+  if (leaf_that_draws)
+    size.SetToMax(leaf_that_draws->bounds());
 
   scoped_refptr<ThumbnailLayer> static_layer =
       tab_content_manager_->GetStaticLayer(id);