Delete scrollCompensationAdjustment.

This feature was added to compensate for fixed-position layers getting
positioned at integer positions but counterscrolled by a full,
fractional amount.  It wound up getting unused because it caused a
performance regression due to defeating the "aborted commit"
optimization during scrolling (every scroll increment with a fractional
change would cause a commit).

There are two ways we can move forward with main-thread fractional
scroll support from here, either 1) have CC automatically compute the
fractional part on the impl thread, or 2) change Blink so that
fixed-position elements don't include the scroll offset in their layout
position at all.  Either way, this scroll compensation feature is dead
code, so we can delete it now.

BUG=414283
CQ_INCLUDE_TRYBOTS=tryserver.blink:linux_blink_rel

Review URL: https://codereview.chromium.org/1385123003

Cr-Commit-Position: refs/heads/master@{#381180}

1 files changed, 0 insertions, 17 deletions

diff --git a/cc/layers/layer.cc b/cc/layers/layer.cc
index dc02b4c..d8d7e51 100644
--- a/cc/layers/layer.cc
+++ b/cc/layers/layer.cc
@@ -835,18 +835,6 @@ void Layer::SetScrollOffset(const gfx::ScrollOffset& scroll_offset) {
   SetNeedsCommit();
 }
 
-void Layer::SetScrollCompensationAdjustment(
-    const gfx::Vector2dF& scroll_compensation_adjustment) {
-  if (scroll_compensation_adjustment_ == scroll_compensation_adjustment)
-    return;
-  scroll_compensation_adjustment_ = scroll_compensation_adjustment;
-  SetNeedsCommit();
-}
-
-gfx::Vector2dF Layer::ScrollCompensationAdjustment() const {
-  return scroll_compensation_adjustment_;
-}
-
 void Layer::SetScrollOffsetFromImplSide(
     const gfx::ScrollOffset& scroll_offset) {
   DCHECK(IsPropertyChangeAllowed());
@@ -1283,7 +1271,6 @@ void Layer::PushPropertiesTo(LayerImpl* layer) {
         ->property_trees()
         ->scroll_tree.synced_scroll_offset(layer->id())
         ->set_clobber_active_value();
-  layer->SetScrollCompensationAdjustment(ScrollCompensationAdjustment());
 
   {
     TRACE_EVENT0("cc", "Layer::PushPropertiesTo::CopyOutputRequests");
@@ -1529,8 +1516,6 @@ void Layer::LayerSpecificPropertiesToProto(proto::LayerProperties* proto) {
   }
 
   ScrollOffsetToProto(scroll_offset_, base->mutable_scroll_offset());
-  Vector2dFToProto(scroll_compensation_adjustment_,
-                   base->mutable_scroll_compensation_adjustment());
 
   // TODO(nyquist): Figure out what to do with CopyRequests.
   // See crbug.com/570374.
@@ -1634,8 +1619,6 @@ void Layer::FromLayerSpecificPropertiesProto(
   }
 
   scroll_offset_ = ProtoToScrollOffset(base.scroll_offset());
-  scroll_compensation_adjustment_ =
-      ProtoToVector2dF(base.scroll_compensation_adjustment());
 
   update_rect_.Union(ProtoToRect(base.update_rect()));
 }