Refactor composite layer mapping to remove redundant conditional.

Bug: 872364
Cq-Include-Trybots: luci.chromium.try:linux_layout_tests_slimming_paint_v2;master.tryserver.blink:linux_trusty_blink_rel
Change-Id: Ib45390dab6120e74d51564760433972f17dae9dc
Reviewed-on: https://chromium-review.googlesource.com/1167882Reviewed-by: Philip Rogers <pdr@chromium.org>
Commit-Queue: Philip Rogers <pdr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#582046}

third_party/blink/renderer/core/page/scrolling/scrolling_coordinator.cc

@@ -529,10 +529,10 @@ bool ScrollingCoordinator::UpdateCompositedScrollOffset(
   return true;
 }
 
-bool ScrollingCoordinator::ScrollableAreaScrollLayerDidChange(
+void ScrollingCoordinator::ScrollableAreaScrollLayerDidChange(
     ScrollableArea* scrollable_area) {
   if (!page_ || !page_->MainFrame())
-    return false;
+    return;
 
   UpdateUserInputScrollable(scrollable_area);
 
@@ -615,7 +615,7 @@ bool ScrollingCoordinator::ScrollableAreaScrollLayerDidChange(
   }
   scrollable_area->LayerForScrollingDidChange(timeline);
 
-  return !!cc_layer;
+  return;
 }
 
 using GraphicsLayerHitTestRects =

third_party/blink/renderer/core/page/scrolling/scrolling_coordinator.h

@@ -139,7 +139,7 @@ class CORE_EXPORT ScrollingCoordinator final
   // blink uses a separate layer. To ensure the compositor scroll layer has the
   // updated scroll container bounds, this needs to be called when the scrolling
   // contents layer is resized.
-  bool ScrollableAreaScrollLayerDidChange(ScrollableArea*);
+  void ScrollableAreaScrollLayerDidChange(ScrollableArea*);
   void ScrollableAreaScrollbarLayerDidChange(ScrollableArea*,
                                              ScrollbarOrientation);
   void UpdateLayerPositionConstraint(PaintLayer*);

third_party/blink/renderer/core/paint/compositing/composited_layer_mapping.cc

@@ -1675,17 +1675,9 @@ void CompositedLayerMapping::UpdateScrollingLayerGeometry(
   if (scrolling_contents_offset != scrolling_contents_offset_ ||
       scroll_size != scrolling_contents_layer_->Size() ||
       scroll_container_size_changed) {
-    bool coordinator_handles_offset = false;
     auto* scrolling_coordinator = owning_layer_.GetScrollingCoordinator();
-    auto* scrollable_area = owning_layer_.GetScrollableArea();
-    if (scrolling_coordinator && scrollable_area) {
-      coordinator_handles_offset =
-          scrolling_coordinator->ScrollableAreaScrollLayerDidChange(
-              scrollable_area);
-    }
-    scrolling_contents_layer_->SetPosition(
-        coordinator_handles_offset ? FloatPoint()
-                                   : FloatPoint(-ToFloatSize(scroll_position)));
+    scrolling_coordinator->ScrollableAreaScrollLayerDidChange(scrollable_area);
+    scrolling_contents_layer_->SetPosition(FloatPoint());
   }
   scrolling_contents_offset_ = scrolling_contents_offset;