cc: Fix invalidation problems in impl-side painting

cc/picture_layer_tiling_set.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/picture_layer_tiling_set.h"
 
 namespace cc {
 
 PictureLayerTilingSet::PictureLayerTilingSet(
     PictureLayerTilingClient * client)
@@ skipping 94 matching lines @@
   bool first_time = current_tiling_ < 0;
 
   if (!*this && !first_time)
     return *this;
 
   if (tiling_iter_)
     ++tiling_iter_;
 
   // Loop until we find a valid place to stop.
   while (true) {
-    while (tiling_iter_ && !tiling_iter_->GetResourceId()) {
+    while (tiling_iter_ && (!*tiling_iter_ || !tiling_iter_->GetResourceId())) {
       missing_region_.Union(tiling_iter_.geometry_rect());
       ++tiling_iter_;
     }
     if (tiling_iter_)
       return *this;
 
     // If the set of current rects for this tiling is done, go to the next
     // tiling and set up to iterate through all of the remaining holes.
     // This will also happen the first time through the loop.
     if (!region_iter_.has_rect()) {
@@ skipping 46 matching lines @@
     const gfx::Transform& current_screen_transform,
     double time_delta) {
   for (size_t i = 0; i < tilings_.size(); ++i) {
     tilings_[i]->UpdateTilePriorities(
         device_viewport, layer_content_scale_x, layer_content_scale_y,
         last_screen_transform, current_screen_transform, time_delta);
   }
 }
 
 }  // namespace cc