Make new-style page scale work on Android.

cc/layer_tree_impl.cc

Index: cc/layer_tree_impl.cc
diff --git a/cc/layer_tree_impl.cc b/cc/layer_tree_impl.cc
index 769639a4091c9dc2e987c7c7b546658329f23489..4650f277d13f7be0d5f7accea0d6662724e01f14 100644
--- a/cc/layer_tree_impl.cc
+++ b/cc/layer_tree_impl.cc
@@ -85,28 +85,21 @@ void LayerTreeImpl::UpdateMaxScrollOffset() {
   if (!root_scroll_layer() || !root_scroll_layer()->children().size())
     return;
 
-  gfx::SizeF view_bounds = device_viewport_size();
-  if (LayerImpl* clip_layer = root_scroll_layer()->parent()) {
-    // Compensate for non-overlay scrollbars.
-    if (clip_layer->masksToBounds())
-      view_bounds = gfx::ScaleSize(clip_layer->bounds(), device_scale_factor());
-  }
-
-  gfx::Size content_bounds = ContentSize();
-  if (settings().pageScalePinchZoomEnabled) {
-    // Pinch with pageScale scrolls entirely in layout space.  ContentSize
-    // returns the bounds including the page scale factor, so calculate the
-    // pre page-scale layout size here.
-    float page_scale_factor = pinch_zoom_viewport().page_scale_factor();
-    content_bounds.set_width(content_bounds.width() / page_scale_factor);
-    content_bounds.set_height(content_bounds.height() / page_scale_factor);
-  } else {
+  gfx::SizeF view_bounds;
+  if (!settings().pageScalePinchZoomEnabled) {
+    view_bounds = device_viewport_size();
+    if (LayerImpl* clip_layer = root_scroll_layer()->parent()) {
+      // Compensate for non-overlay scrollbars.
+      if (clip_layer->masksToBounds())
+        view_bounds = gfx::ScaleSize(clip_layer->bounds(), device_scale_factor());
+    }
     view_bounds.Scale(1 / pinch_zoom_viewport().page_scale_delta());
+  } else {
+    view_bounds = layout_viewport_size();
   }
 
-  gfx::Vector2dF max_scroll = gfx::Rect(content_bounds).bottom_right() -
+  gfx::Vector2dF max_scroll = gfx::Rect(ScrollableSize()).bottom_right() -
       gfx::RectF(view_bounds).bottom_right();
-  max_scroll.Scale(1 / device_scale_factor());
 
   // The viewport may be larger than the contents in some cases, such as
   // having a vertical scrollbar but no horizontal overflow.
@@ -175,12 +168,10 @@ const LayerTreeImpl::LayerList& LayerTreeImpl::RenderSurfaceLayerList() const {
   return render_surface_layer_list_;
 }
 
-gfx::Size LayerTreeImpl::ContentSize() const {
-  // TODO(aelias): Hardcoding the first child here is weird. Think of
-  // a cleaner way to get the contentBounds on the Impl side.
+gfx::Size LayerTreeImpl::ScrollableSize() const {
   if (!root_scroll_layer() || root_scroll_layer()->children().empty())
     return gfx::Size();
-  return root_scroll_layer()->children()[0]->contentBounds();
+  return root_scroll_layer()->children()[0]->bounds();
 }
 
 LayerImpl* LayerTreeImpl::LayerById(int id) {