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

cc/layers/picture_layer_impl.cc

Index: cc/layers/picture_layer_impl.cc
diff --git a/cc/layers/picture_layer_impl.cc b/cc/layers/picture_layer_impl.cc
index 4bb23b6d8da1610ed3efb702e757ec1efb30e1fb..9b94f43ded3e7abea003d1b22c0b281995b0a6bf 100644
--- a/cc/layers/picture_layer_impl.cc
+++ b/cc/layers/picture_layer_impl.cc
@@ -1249,9 +1249,10 @@ void PictureLayerImpl::UpdateIdealScales() {
   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,