[PE] Reduce copies of LayoutRect in PaintLayerClipper.

Bug: 798378
Cq-Include-Trybots: master.tryserver.blink:linux_trusty_blink_rel;master.tryserver.chromium.linux:linux_layout_tests_slimming_paint_v2
Change-Id: Ic3c0b29430b06e76a3c81e654bc780e4a969592d
Reviewed-on: https://chromium-review.googlesource.com/880403
Commit-Queue: Chris Harrelson <chrishtr@chromium.org>
Reviewed-by: Stephen Chenney <schenney@chromium.org>
Cr-Commit-Position: refs/heads/master@{#532031}

third_party/WebKit/Source/core/layout/LayoutBox.cpp

@@ -1943,12 +1943,24 @@ PaintInvalidationReason LayoutBox::InvalidatePaint(
 LayoutRect LayoutBox::OverflowClipRect(
     const LayoutPoint& location,
     OverlayScrollbarClipBehavior overlay_scrollbar_clip_behavior) const {
-  if (RootScrollerUtil::IsEffective(*this))
-    return View()->ViewRect();
+  LayoutRect clip_rect;
+  CalculateOverflowClipRect(location, overlay_scrollbar_clip_behavior,
+                            clip_rect);
+  return clip_rect;
+}
+
+void LayoutBox::CalculateOverflowClipRect(
+    const LayoutPoint& location,
+    OverlayScrollbarClipBehavior overlay_scrollbar_clip_behavior,
+    LayoutRect& clip_rect) const {
+  if (RootScrollerUtil::IsEffective(*this)) {
+    clip_rect = View()->ViewRect();
+    return;
+  }
 
   // FIXME: When overflow-clip (CSS3) is implemented, we'll obtain the property
   // here.
-  LayoutRect clip_rect = BorderBoxRect();
+  clip_rect = BorderBoxRect();
   clip_rect.SetLocation(location + clip_rect.Location() +
                         LayoutSize(BorderLeft(), BorderTop()));
   clip_rect.SetSize(clip_rect.Size() -
@@ -1959,8 +1971,6 @@ LayoutRect LayoutBox::OverflowClipRect(
 
   if (HasControlClip())
     clip_rect.Intersect(ControlClipRect(location));
-
-  return clip_rect;
 }
 
 void LayoutBox::ExcludeScrollbars(

third_party/WebKit/Source/core/layout/LayoutBox.h

@@ -1046,12 +1046,18 @@ class CORE_EXPORT LayoutBox : public LayoutBoxModelObject {
   // control clips or contain: paint.
   virtual bool ShouldClipOverflow() const;
 
-  // Returns the intersection of all overflow clips which apply.
-  virtual LayoutRect OverflowClipRect(
+  // Returns same value as ApplyOverflowClipRect sets on its third argument.
+  LayoutRect OverflowClipRect(
       const LayoutPoint& location,
       OverlayScrollbarClipBehavior = kIgnorePlatformOverlayScrollbarSize) const;
   LayoutRect ClipRect(const LayoutPoint& location) const;
 
+  // Sets |clip_rect| to be equal to the bounds of the element, intersected
+  // with all overflow clips which aply.
+  virtual void CalculateOverflowClipRect(const LayoutPoint& location,
+                                         OverlayScrollbarClipBehavior,
+                                         LayoutRect& clip_rect) const;
+
   // Returns the combination of overflow clip, contain: paint clip and CSS clip
   // for this object.
   LayoutRect ClippingRect(const LayoutPoint& location) const;

third_party/WebKit/Source/core/layout/LayoutTable.cpp

@@ -1473,19 +1473,21 @@ LayoutUnit LayoutTable::FirstLineBoxBaseline() const {
   return LayoutUnit(-1);
 }
 
-LayoutRect LayoutTable::OverflowClipRect(
+void LayoutTable::CalculateOverflowClipRect(
     const LayoutPoint& location,
-    OverlayScrollbarClipBehavior overlay_scrollbar_clip_behavior) const {
+    OverlayScrollbarClipBehavior overlay_scrollbar_clip_behavior,
+    LayoutRect& rect) const {
   if (ShouldCollapseBorders()) {
     // Though the outer halves of the collapsed borders are considered as the
     // the border area of the table by means of the box model, they are actually
     // contents of the table and should not be clipped off. The overflow clip
     // rect is BorderBoxRect() + location.
-    return LayoutRect(location, Size());
+    rect = LayoutRect(location, Size());
+    return;
   }
 
-  LayoutRect rect =
-      LayoutBlock::OverflowClipRect(location, overlay_scrollbar_clip_behavior);
+  LayoutBlock::CalculateOverflowClipRect(location,
+                                         overlay_scrollbar_clip_behavior, rect);
 
   // If we have a caption, expand the clip to include the caption.
   // FIXME: Technically this is wrong, but it's virtually impossible to fix this
@@ -1503,8 +1505,6 @@ LayoutRect LayoutTable::OverflowClipRect(
       rect.SetX(location.X());
     }
   }
-
-  return rect;
 }
 
 bool LayoutTable::NodeAtPoint(HitTestResult& result,

third_party/WebKit/Source/core/layout/LayoutTable.h

@@ -470,10 +470,9 @@ class CORE_EXPORT LayoutTable final : public LayoutBlock {
   LayoutUnit ConvertStyleLogicalHeightToComputedHeight(
       const Length& style_logical_height) const;
 
-  LayoutRect OverflowClipRect(
-      const LayoutPoint& location,
-      OverlayScrollbarClipBehavior =
-          kIgnorePlatformOverlayScrollbarSize) const override;
+  void CalculateOverflowClipRect(const LayoutPoint& location,
+                                 OverlayScrollbarClipBehavior,
+                                 LayoutRect&) const override;
 
   void AddOverflowFromChildren() override;
 

third_party/WebKit/Source/core/layout/LayoutView.cpp

@@ -624,19 +624,20 @@ LayoutRect LayoutView::ViewRect() const {
   return LayoutRect();
 }
 
-LayoutRect LayoutView::OverflowClipRect(
+void LayoutView::CalculateOverflowClipRect(
     const LayoutPoint& location,
-    OverlayScrollbarClipBehavior overlay_scrollbar_clip_behavior) const {
-  LayoutRect rect = ViewRect();
-  if (rect.IsEmpty())
-    return LayoutBox::OverflowClipRect(location,
-                                       overlay_scrollbar_clip_behavior);
+    OverlayScrollbarClipBehavior overlay_scrollbar_clip_behavior,
+    LayoutRect& rect) const {
+  rect = ViewRect();
+  if (rect.IsEmpty()) {
+    LayoutBox::CalculateOverflowClipRect(location,
+                                         overlay_scrollbar_clip_behavior, rect);
+    return;
+  }
 
   rect.SetLocation(location);
   if (HasOverflowClip())
     ExcludeScrollbars(rect, overlay_scrollbar_clip_behavior);
-
-  return rect;
 }
 
 void LayoutView::CalculateScrollbarModes(ScrollbarMode& h_mode,

third_party/WebKit/Source/core/layout/LayoutView.h

@@ -153,10 +153,10 @@ class CORE_EXPORT LayoutView final : public LayoutBlockFlow {
                      MapCoordinatesFlags mode = 0) const override;
 
   LayoutRect ViewRect() const override;
-  LayoutRect OverflowClipRect(
-      const LayoutPoint& location,
-      OverlayScrollbarClipBehavior =
-          kIgnorePlatformOverlayScrollbarSize) const override;
+
+  void CalculateOverflowClipRect(const LayoutPoint& location,
+                                 OverlayScrollbarClipBehavior,
+                                 LayoutRect&) const override;
 
   void CalculateScrollbarModes(ScrollbarMode& h_mode,
                                ScrollbarMode& v_mode) const;

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

@@ -50,6 +50,8 @@ class ClipRect {
     has_radius_ = rect.HasRadius();
   }
 
+  LayoutRect& MutableRect() { return rect_; }
+
   const LayoutRect& Rect() const { return rect_; }
 
   bool HasRadius() const { return has_radius_; }

third_party/WebKit/Source/core/paint/PaintLayerClipper.cpp

@@ -331,10 +331,10 @@ void PaintLayerClipper::CalculateRectsWithGeometryMapper(
 
   if (ShouldClipOverflow(context)) {
     LayoutBoxModelObject& layout_object = layer_.GetLayoutObject();
-    foreground_rect =
-        ToLayoutBox(layout_object)
-            .OverflowClipRect(layer_bounds.Location(),
-                              context.overlay_scrollbar_clip_behavior);
+    ToLayoutBox(layout_object)
+        .CalculateOverflowClipRect(layer_bounds.Location(),
+                                   context.overlay_scrollbar_clip_behavior,
+                                   foreground_rect.MutableRect());
     if (layout_object.StyleRef().HasBorderRadius())
       foreground_rect.SetHasRadius(true);
     foreground_rect.Intersect(background_rect);