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}

5 files changed, 0 insertions, 35 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()));
 }
diff --git a/cc/layers/layer.h b/cc/layers/layer.h
index 5cb2a25..64540492 100644
--- a/cc/layers/layer.h
+++ b/cc/layers/layer.h
@@ -253,9 +253,6 @@ class CC_EXPORT Layer : public base::RefCounted<Layer> {
   }
 
   void SetScrollOffset(const gfx::ScrollOffset& scroll_offset);
-  void SetScrollCompensationAdjustment(
-      const gfx::Vector2dF& scroll_compensation_adjustment);
-  gfx::Vector2dF ScrollCompensationAdjustment() const;
 
   gfx::ScrollOffset scroll_offset() const { return scroll_offset_; }
   void SetScrollOffsetFromImplSide(const gfx::ScrollOffset& scroll_offset);
@@ -653,7 +650,6 @@ class CC_EXPORT Layer : public base::RefCounted<Layer> {
   gfx::Size bounds_;
 
   gfx::ScrollOffset scroll_offset_;
-  gfx::Vector2dF scroll_compensation_adjustment_;
   // This variable indicates which ancestor layer (if any) whose size,
   // transformed relative to this layer, defines the maximum scroll offset for
   // this layer.
diff --git a/cc/layers/layer_impl.cc b/cc/layers/layer_impl.cc
index 753beca..b3a3fc4 100644
--- a/cc/layers/layer_impl.cc
+++ b/cc/layers/layer_impl.cc
@@ -539,8 +539,6 @@ void LayerImpl::PushPropertiesTo(LayerImpl* layer) {
   layer->set_user_scrollable_horizontal(user_scrollable_horizontal_);
   layer->set_user_scrollable_vertical(user_scrollable_vertical_);
 
-  layer->SetScrollCompensationAdjustment(scroll_compensation_adjustment_);
-
   layer->Set3dSortingContextId(sorting_context_id_);
   layer->SetNumDescendantsThatDrawContent(num_descendants_that_draw_content_);
 
diff --git a/cc/layers/layer_impl.h b/cc/layers/layer_impl.h
index 1bc1bc6..b9f8c77 100644
--- a/cc/layers/layer_impl.h
+++ b/cc/layers/layer_impl.h
@@ -431,12 +431,6 @@ class CC_EXPORT LayerImpl {
   gfx::ScrollOffset MaxScrollOffset() const;
   gfx::ScrollOffset ClampScrollOffsetToLimits(gfx::ScrollOffset offset) const;
   gfx::Vector2dF ClampScrollToMaxScrollOffset();
-  void SetScrollCompensationAdjustment(const gfx::Vector2dF& scroll_offset) {
-    scroll_compensation_adjustment_ = scroll_offset;
-  }
-  gfx::Vector2dF ScrollCompensationAdjustment() const {
-    return scroll_compensation_adjustment_;
-  }
 
   // Returns the delta of the scroll that was outside of the bounds of the
   // initial scroll
@@ -735,8 +729,6 @@ class CC_EXPORT LayerImpl {
 
   LayerPositionConstraint position_constraint_;
 
-  gfx::Vector2dF scroll_compensation_adjustment_;
-
   int num_descendants_that_draw_content_;
 
   gfx::Rect clip_rect_in_target_space_;
diff --git a/cc/layers/layer_unittest.cc b/cc/layers/layer_unittest.cc
index 59a2b5c..73aebe9 100644
--- a/cc/layers/layer_unittest.cc
+++ b/cc/layers/layer_unittest.cc
@@ -180,8 +180,6 @@ class LayerSerializationTest : public testing::Test {
               dest->user_scrollable_horizontal_);
     EXPECT_EQ(src->user_scrollable_vertical_, dest->user_scrollable_vertical_);
     EXPECT_EQ(src->scroll_offset_, dest->scroll_offset_);
-    EXPECT_EQ(src->scroll_compensation_adjustment_,
-              dest->scroll_compensation_adjustment_);
     EXPECT_EQ(update_rect, dest->update_rect_);
 
     if (src->scroll_parent_) {
@@ -287,7 +285,6 @@ class LayerSerializationTest : public testing::Test {
     layer->user_scrollable_horizontal_ = false;
     layer->user_scrollable_vertical_ = true;
     layer->scroll_offset_ = gfx::ScrollOffset(3, 14);
-    layer->scroll_compensation_adjustment_ = gfx::Vector2dF(6.28f, 3.14f);
     layer->update_rect_ = gfx::Rect(14, 15);
 
     VerifyBaseLayerPropertiesSerializationAndDeserialization(layer.get());
@@ -337,7 +334,6 @@ class LayerSerializationTest : public testing::Test {
     layer->user_scrollable_horizontal_ = !layer->user_scrollable_horizontal_;
     layer->user_scrollable_vertical_ = !layer->user_scrollable_vertical_;
     layer->scroll_offset_ = gfx::ScrollOffset(3, 14);
-    layer->scroll_compensation_adjustment_ = gfx::Vector2dF(6.28f, 3.14f);
     layer->update_rect_ = gfx::Rect(14, 15);
 
     VerifyBaseLayerPropertiesSerializationAndDeserialization(layer.get());