cc: Fix size_t to int truncations in tiles/ and trees/

cc/trees/occlusion_tracker.cc

 // Copyright 2012 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/trees/occlusion_tracker.h"
 
 #include <algorithm>
 
 #include "cc/base/math_util.h"
 #include "cc/base/region.h"
@@ skipping 195 matching lines @@
   bool entering_root_target = new_target->parent() == NULL;
 
   bool copy_outside_occlusion_forward =
       stack_.size() > 1 &&
       !entering_unoccluded_subtree &&
       have_transform_from_screen_to_new_target &&
       !entering_root_target;
   if (!copy_outside_occlusion_forward)
     return;
 
-  int last_index = stack_.size() - 1;
+  size_t last_index = stack_.size() - 1;
   gfx::Transform old_target_to_new_target_transform(
       inverse_new_target_screen_space_transform,
       old_target->render_surface()->screen_space_transform());
   stack_[last_index].occlusion_from_outside_target =
       TransformSurfaceOpaqueRegion<typename LayerType::RenderSurfaceType>(
           stack_[last_index - 1].occlusion_from_outside_target,
           false,
           gfx::Rect(),
           old_target_to_new_target_transform);
   stack_[last_index].occlusion_from_outside_target.Union(
@@ skipping 84 matching lines @@
 
     occlusion_rect.Inset(shrink_left, shrink_top, shrink_right, shrink_bottom);
 
     occlusion_from_inside_target->Union(occlusion_rect);
   }
 }
 
 template <typename LayerType>
 void OcclusionTracker<LayerType>::LeaveToRenderTarget(
     const LayerType* new_target) {
-  int last_index = stack_.size() - 1;
+  DCHECK(!stack_.empty());
+  size_t last_index = stack_.size() - 1;
   bool surface_will_be_at_top_after_pop =
       stack_.size() > 1 && stack_[last_index - 1].target == new_target;
 
   // We merge the screen occlusion from the current RenderSurfaceImpl subtree
   // out to its parent target RenderSurfaceImpl. The target occlusion can be
   // merged out as well but needs to be transformed to the new target.
 
   const LayerType* old_target = stack_[last_index].target;
   const typename LayerType::RenderSurfaceType* old_surface =
       old_target->render_surface();
@@ skipping 145 matching lines @@
   for (size_t i = 0; i < occluded.GetRegionComplexity(); ++i)
     visible_region.Subtract(occluded.GetRect(i));
   return visible_region;
 }
 
 // Instantiate (and export) templates here for the linker.
 template class OcclusionTracker<Layer>;
 template class OcclusionTracker<LayerImpl>;
 
 }  // namespace cc