cc: Don't rasterize large layers at maximum scale before scale animations

cc/layers/picture_layer_impl.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/layers/picture_layer_impl.h"
 
 #include <algorithm>
 #include <limits>
 
 #include "base/time/time.h"
@@ skipping 1093 matching lines @@
     raster_contents_scale_ = SnappedContentsScale(desired_contents_scale);
     raster_page_scale_ =
         raster_contents_scale_ / raster_device_scale_ / raster_source_scale_;
   }
 
   raster_contents_scale_ =
       std::max(raster_contents_scale_, MinimumContentsScale());
 
   // Since we're not re-rasterizing during animation, rasterize at the maximum
   // scale that will occur during the animation, if the maximum scale is
-  // known.
+  // known. However, to avoid excessive memory use, don't rasterize at a scale
+  // at which this layer would become larger than the viewport.
   if (draw_properties().screen_space_transform_is_animating) {
+    bool can_raster_at_maximum_scale = false;
     if (draw_properties().maximum_animation_contents_scale > 0.f) {
+      gfx::Size bounds_at_maximum_scale = gfx::ToCeiledSize(gfx::ScaleSize(
+          bounds(), draw_properties().maximum_animation_contents_scale));
+      if (bounds_at_maximum_scale.GetArea() <=
+          layer_tree_impl()->device_viewport_size().GetArea())
+        can_raster_at_maximum_scale = true;
+    }
+    if (can_raster_at_maximum_scale) {
       raster_contents_scale_ =
           std::max(raster_contents_scale_,
                    draw_properties().maximum_animation_contents_scale);
     } else {
       raster_contents_scale_ =
           std::max(raster_contents_scale_,
                    1.f * ideal_page_scale_ * ideal_device_scale_);
     }
   }
 
@@ skipping 502 matching lines @@
   return iterator_index_ < iterators_.size();
 }
 
 bool PictureLayerImpl::LayerEvictionTileIterator::IsCorrectType(
     PictureLayerTiling::TilingEvictionTileIterator* it) const {
   return it->get_type() == iteration_stage_ &&
          (**it)->required_for_activation() == required_for_activation_;
 }
 
 }  // namespace cc