[CI] Refactor FragmentPaintPropertyTreeBuilder::UpdateForPaintOffsetTranslation

- Combine ApplyPaintOffsetTranslation into the method. This avoids
  the ambiguous function name.

- Remove unrelated context_.absolute_position.paint_offset and
  context_.fixed_position.paint_offset updates for LayoutView from
  the function. They will be done by existing code in
  UpdateOutOfFlowContext().

Cq-Include-Trybots: master.tryserver.blink:linux_trusty_blink_rel;master.tryserver.chromium.linux:linux_layout_tests_slimming_paint_v2
Change-Id: I3cd103cf5d7614f144ebfcf30c3aaa7a75db76f6
Reviewed-on: https://chromium-review.googlesource.com/1080014Reviewed-by: Philip Rogers <pdr@chromium.org>
Commit-Queue: Xianzhu Wang <wangxianzhu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#563139}

third_party/blink/renderer/core/paint/paint_property_tree_builder.cc

@@ -252,8 +252,11 @@ static bool NeedsPaintOffsetTranslation(const LayoutObject& object) {
   return false;
 }
 
-IntPoint ApplyPaintOffsetTranslation(const LayoutObject& object,
-                                     LayoutPoint& paint_offset) {
+void FragmentPaintPropertyTreeBuilder::UpdateForPaintOffsetTranslation(
+    base::Optional<IntPoint>& paint_offset_translation) {
+  if (!NeedsPaintOffsetTranslation(object_))
+    return;
+
   // We should use the same subpixel paint offset values for snapping
   // regardless of whether a transform is present. If there is a transform
   // we round the paint offset but keep around the residual fractional
@@ -261,35 +264,21 @@ IntPoint ApplyPaintOffsetTranslation(const LayoutObject& object,
   // called "subpixel accumulation". For more information, see
   // PaintLayer::subpixelAccumulation() and
   // PaintLayerPainter::paintFragmentByApplyingTransform.
-  IntPoint paint_offset_translation = RoundedIntPoint(paint_offset);
+  paint_offset_translation = RoundedIntPoint(context_.current.paint_offset);
   LayoutPoint fractional_paint_offset =
-      LayoutPoint(paint_offset - paint_offset_translation);
+      LayoutPoint(context_.current.paint_offset - *paint_offset_translation);
   if (fractional_paint_offset != LayoutPoint()) {
     // If the object has a non-translation transform, discard the fractional
     // paint offset which can't be transformed by the transform.
     TransformationMatrix matrix;
-    object.StyleRef().ApplyTransform(
+    object_.StyleRef().ApplyTransform(
         matrix, LayoutSize(), ComputedStyle::kExcludeTransformOrigin,
         ComputedStyle::kIncludeMotionPath,
         ComputedStyle::kIncludeIndependentTransformProperties);
     if (!matrix.IsIdentityOrTranslation())
       fractional_paint_offset = LayoutPoint();
   }
-  paint_offset = fractional_paint_offset;
-  return paint_offset_translation;
-}
-
-void FragmentPaintPropertyTreeBuilder::UpdateForPaintOffsetTranslation(
-    base::Optional<IntPoint>& paint_offset_translation) {
-  if (!NeedsPaintOffsetTranslation(object_))
-    return;
-
-  paint_offset_translation =
-      ApplyPaintOffsetTranslation(object_, context_.current.paint_offset);
-  if (object_.IsLayoutView()) {
-    context_.absolute_position.paint_offset = context_.current.paint_offset;
-    context_.fixed_position.paint_offset = context_.current.paint_offset;
-  }
+  context_.current.paint_offset = fractional_paint_offset;
 }
 
 void FragmentPaintPropertyTreeBuilder::UpdatePaintOffsetTranslation(