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

cc/trees/property_tree.cc

 // Copyright 2014 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 <set>
 #include <vector>
 
 #include "base/logging.h"
 #include "cc/base/math_util.h"
 #include "cc/trees/property_tree.h"
@@ skipping 221 matching lines @@
     // 4. When walking up the ancestor chain from F, the first node with a
     // smaller id than S will be T, the lowest common ancestor of these nodes.
     // We compute the transform from T to S here, and then from F to T in the
     // loop below.
     DCHECK(IsDescendant(dest_id, current->id));
     CombineInversesBetween(current->id, dest_id, &combined_transform);
     DCHECK(combined_transform.IsApproximatelyIdentityOrTranslation(
         SkDoubleToMScalar(1e-4)));
   }
 
-  for (int i = source_to_destination.size() - 1; i >= 0; i--) {
-    const TransformNode* node = Node(source_to_destination[i]);
+  for (size_t i = 0; i < source_to_destination.size(); ++i) {
+    size_t index = source_to_destination.size() - 1 - i;
+    const TransformNode* node = Node(source_to_destination[index]);
     if (node->data.flattens_inherited_transform)
       combined_transform.FlattenTo2d();
     combined_transform.PreconcatTransform(node->data.to_parent);
   }
 
   transform->ConcatTransform(combined_transform);
   return true;
 }
 
 bool TransformTree::CombineInversesBetween(int source_id,
@@ skipping 134 matching lines @@
   node->data.from_screen.matrix().postTranslate(-translation.x(),
                                                 -translation.y(), 0);
 
   node->data.scroll_snap = translation;
 }
 
 PropertyTrees::PropertyTrees() : needs_rebuild(true), sequence_number(0) {
 }
 
 }  // namespace cc