[Master/Overview CL] Make PageScaleFactor work for oopif subframe.

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 <stddef.h>
 #include <stdint.h>
 
 #include <algorithm>
@@ skipping 1231 matching lines @@
       settings.skewport_extrapolation_limit_in_screen_pixels,
       settings.max_preraster_distance_in_screen_pixels);
 }
 
 void PictureLayerImpl::UpdateIdealScales() {
   DCHECK(CanHaveTilings());
 
   float min_contents_scale = MinimumContentsScale();
   DCHECK_GT(min_contents_scale, 0.f);
 
-  ideal_page_scale_ = IsAffectedByPageScale()
-                          ? layer_tree_impl()->current_page_scale_factor()
-                          : 1.f;
+  ideal_page_scale_ =
+      (!layer_tree_impl()->PageScaleLayer() || IsAffectedByPageScale())

[Ian Vollick, 2016/10/14 19:40:30]

So we take the current page scale factor if we don't have a page scale layer at
all (which is true for subframes today), or we know we're affected by it? (And
the rest of your CL ensures that the page scale is plumbed so that
current_page_scale_factor will have what you need?)

This does seem plausible, but please get the opinion of people that know more
about raster scale.

+          ? layer_tree_impl()->current_page_scale_factor()
+          : 1.f;
   ideal_device_scale_ = layer_tree_impl()->device_scale_factor();
   ideal_contents_scale_ =
       std::min(kMaxIdealContentsScale,
                std::max(GetIdealContentsScale(), min_contents_scale));
   ideal_source_scale_ =
       ideal_contents_scale_ / ideal_page_scale_ / ideal_device_scale_;
   UMA_HISTOGRAM_CUSTOM_COUNTS("Renderer4.IdealContentsScale",
                               ideal_contents_scale_, 1, 10000, 50);
 }
 
@@ skipping 70 matching lines @@
 bool PictureLayerImpl::IsOnActiveOrPendingTree() const {
   return !layer_tree_impl()->IsRecycleTree();
 }
 
 bool PictureLayerImpl::HasValidTilePriorities() const {
   return IsOnActiveOrPendingTree() &&
          is_drawn_render_surface_layer_list_member();
 }
 
 }  // namespace cc