Avoid false-positives of paint offset change detection

third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilder.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef PaintPropertyTreeBuilder_h
 #define PaintPropertyTreeBuilder_h
 
 #include "platform/geometry/LayoutPoint.h"
 #include "platform/graphics/paint/ClipPaintPropertyNode.h"
 #include "platform/graphics/paint/EffectPaintPropertyNode.h"
 #include "platform/graphics/paint/ScrollPaintPropertyNode.h"
 #include "platform/graphics/paint/TransformPaintPropertyNode.h"
 #include "wtf/RefPtr.h"
 
 namespace blink {
 
 class FrameView;
+class LayoutBoxModelObject;
 class LayoutObject;
 
 // The context for PaintPropertyTreeBuilder.
 // It's responsible for bookkeeping tree state in other order, for example, the
 // most recent position container seen.
 struct PaintPropertyTreeBuilderContext {
   // State that propagates on the containing block chain (and so is adjusted
   // when an absolute or fixed position object is encountered).
   struct ContainingBlockContext {
     // The combination of a transform and paint offset describes a linear space.
@@ skipping 64 matching lines @@
 // animation, mask, filter, ... etc.
 // It expects to be invoked for each layout tree node in DOM order during
 // InPrePaint phase.
 class PaintPropertyTreeBuilder {
  public:
   PaintPropertyTreeBuilderContext setupInitialContext();
   // Update the paint properties for a frame and ensure the context is up to
   // date.
   void updateProperties(FrameView&, PaintPropertyTreeBuilderContext&);
 
-  // Update the context to account for positioning. No paint properties are
-  // updated but this can affect the current paint offset which will force a
-  // subtree update.
+  // Update the context to account for positioning. Paint offset and
+  // paint offset translation (if needed) are updated. If paint offset changes
+  // we will force subtree update.
   void updateContextForBoxPosition(const LayoutObject&,
                                    PaintPropertyTreeBuilderContext&);
 
   // Update the paint properties that affect this object (e.g., properties like
   // paint offset translation) and ensure the context is up to date. Also
   // handles updating the object's paintOffset.
   void updatePropertiesForSelf(const LayoutObject&,
                                PaintPropertyTreeBuilderContext&);
   // Update the paint properties that affect children of this object (e.g.,
   // scroll offset transform) and ensure the context is up to date.
   void updatePropertiesForChildren(const LayoutObject&,
                                    PaintPropertyTreeBuilderContext&);
 
  private:
+  ALWAYS_INLINE static void updatePaintOffset(const LayoutBoxModelObject&,
+                                              PaintPropertyTreeBuilderContext&);
   ALWAYS_INLINE static void updatePaintOffsetTranslation(
-      const LayoutObject&,
+      const LayoutBoxModelObject&,
       PaintPropertyTreeBuilderContext&);
   ALWAYS_INLINE static void updateTransform(const LayoutObject&,
                                             PaintPropertyTreeBuilderContext&);
   ALWAYS_INLINE static void updateTransformForNonRootSVG(
       const LayoutObject&,
       PaintPropertyTreeBuilderContext&);
   ALWAYS_INLINE static void updateEffect(const LayoutObject&,
                                          PaintPropertyTreeBuilderContext&);
   ALWAYS_INLINE static void updateCssClip(const LayoutObject&,
                                           PaintPropertyTreeBuilderContext&);
@@ skipping 15 matching lines @@
       const LayoutObject&,
       PaintPropertyTreeBuilderContext&);
   ALWAYS_INLINE static void updateOutOfFlowContext(
       const LayoutObject&,
       PaintPropertyTreeBuilderContext&);
 };
 
 }  // namespace blink
 
 #endif  // PaintPropertyTreeBuilder_h