Removed pinch viewport scroll offset distribution

The associated change in Blink makes the pinch viewport a proper
ScrollableArea meaning the normal path for synchronizing layer scroll
offsets is used.

This is a 2 sided patch, the other CL:
https://codereview.chromium.org/199253002/

BUG=349941

Review URL: https://codereview.chromium.org/210543002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@260105 0039d316-1c4b-4281-b951-d872f2087c98

cc/cc_tests.gyp

@@ -103,7 +103,6 @@
       'trees/layer_tree_host_unittest_delegated.cc',
       'trees/layer_tree_host_unittest_occlusion.cc',
       'trees/layer_tree_host_unittest_picture.cc',
-      'trees/layer_tree_host_unittest_pinch_zoom.cc',
       'trees/layer_tree_host_unittest_scroll.cc',
       'trees/layer_tree_host_unittest_video.cc',
       'trees/occlusion_tracker_unittest.cc',

cc/layers/layer.cc

@@ -674,11 +674,6 @@ void Layer::RemoveClipChild(Layer* child) {
 void Layer::SetScrollOffset(gfx::Vector2d scroll_offset) {
   DCHECK(IsPropertyChangeAllowed());
 
-  if (layer_tree_host()) {
-    scroll_offset = layer_tree_host()->DistributeScrollOffsetToViewports(
-        scroll_offset, this);
-  }
-
   if (scroll_offset_ == scroll_offset)
     return;
   scroll_offset_ = scroll_offset;

cc/trees/layer_tree_host.cc

@@ -1059,50 +1059,6 @@ void LayerTreeHost::ApplyScrollAndScale(const ScrollAndScaleSet& info) {
   }
 }
 
-gfx::Vector2d LayerTreeHost::DistributeScrollOffsetToViewports(
-    const gfx::Vector2d offset,
-    Layer* layer) {
-  DCHECK(layer);
-  if (layer != outer_viewport_scroll_layer_.get())
-    return offset;
-
-  gfx::Vector2d inner_viewport_offset =
-      inner_viewport_scroll_layer_->scroll_offset();
-  gfx::Vector2d outer_viewport_offset =
-      outer_viewport_scroll_layer_->scroll_offset();
-
-  if (offset == inner_viewport_offset + outer_viewport_offset) {
-    // In this case, nothing should change, so we just return to the outer
-    // viewport the offset is already has.
-    return outer_viewport_offset;
-  }
-
-  // In the spirit of document-scrolls-first, we always want any change to
-  // go to the outer viewport first.
-  gfx::Vector2d max_outer_viewport_scroll_offset =
-      outer_viewport_scroll_layer_->MaxScrollOffset();
-  gfx::Vector2d max_inner_viewport_scroll_offset =
-      inner_viewport_scroll_layer_->MaxScrollOffset();
-
-  // TODO(bokan): This trips on zoom-out due to how Blink orders scale-scroll.
-  //              Disabled until that's sorted out: crbug.com/336574
-  // gfx::Vector2d total_max_scroll_offset =
-  //    max_outer_viewport_scroll_offset + max_inner_viewport_scroll_offset;
-  // DCHECK(total_max_scroll_offset.x() >= offset.x() &&
-  //       total_max_scroll_offset.y() >= offset.y());
-
-  outer_viewport_offset = offset - inner_viewport_offset;
-  outer_viewport_offset.SetToMin(max_outer_viewport_scroll_offset);
-  outer_viewport_offset.SetToMax(gfx::Vector2d());
-
-  inner_viewport_offset = offset - outer_viewport_offset;
-  inner_viewport_offset.SetToMin(max_inner_viewport_scroll_offset);
-  inner_viewport_offset.SetToMax(gfx::Vector2d());
-  inner_viewport_scroll_layer_->SetScrollOffset(inner_viewport_offset);
-
-  return outer_viewport_offset;
-}
-
 void LayerTreeHost::StartRateLimiter() {
   if (animating_)
     return;

cc/trees/layer_tree_host.h

@@ -239,9 +239,6 @@ class CC_EXPORT LayerTreeHost {
                                base::TimeDelta duration);
 
   void ApplyScrollAndScale(const ScrollAndScaleSet& info);
-  gfx::Vector2d DistributeScrollOffsetToViewports(const gfx::Vector2d offset,
-                                                  Layer* layer);
-
   void SetImplTransform(const gfx::Transform& transform);
 
   // Virtual for tests.