Optimize the pre-paint tree walk and ClipRects

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

 /*
  * Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011, 2012 Apple Inc. All rights
  * reserved.
  *
  * Portions are Copyright (C) 1998 Netscape Communications Corporation.
  *
  * Other contributors:
  *   Robert O'Callahan <roc+@cs.cmu.edu>
  *   David Baron <dbaron@fas.harvard.edu>
  *   Christian Biesinger <cbiesinger@web.de>
@@ skipping 110 matching lines @@
       m_layer.clipRectsCache()->get(context.cacheSlot());
   // FIXME: We used to ASSERT that we always got a consistent root layer.
   // We should add a test that has an inconsistent root. See
   // http://crbug.com/366118 for an example.
   if (context.rootLayer != entry.root)
     return 0;
 #if DCHECK_IS_ON()
   DCHECK(entry.overlayScrollbarClipBehavior ==
          context.overlayScrollbarClipBehavior);
 #endif
-  return entry.clipRects.get();
+  return &entry.clipRects;
 }
 
 ClipRects& PaintLayerClipper::storeClipRectsInCache(
     const ClipRectsContext& context,
     ClipRects* parentClipRects,
     const ClipRects& clipRects) const {
   ClipRectsCache::Entry& entry =
       m_layer.ensureClipRectsCache().get(context.cacheSlot());
   entry.root = context.rootLayer;
 #if DCHECK_IS_ON()
   entry.overlayScrollbarClipBehavior = context.overlayScrollbarClipBehavior;
 #endif
   if (parentClipRects) {
     // If our clip rects match the clip rects of our parent, we share storage.
     if (clipRects == *parentClipRects) {
-      entry.clipRects = parentClipRects;
+      entry.clipRects = *parentClipRects;
       return *parentClipRects;
     }
   }
-  entry.clipRects = ClipRects::create(clipRects);
-  return *entry.clipRects;
+  entry.clipRects = clipRects;
+  return entry.clipRects;
 }
 
 ClipRects& PaintLayerClipper::getClipRects(
     const ClipRectsContext& context) const {
   DCHECK(!m_geometryMapper);
   if (ClipRects* result = clipRectsIfCached(context))
     return *result;
   // Note that it's important that we call getClipRects on our parent
   // before we call calculateClipRects so that calculateClipRects will hit
   // the cache.
   ClipRects* parentClipRects = nullptr;
   if (context.rootLayer != &m_layer && m_layer.parent()) {
     parentClipRects =
         &PaintLayerClipper(*m_layer.parent(), nullptr).getClipRects(context);
   }
-  RefPtr<ClipRects> clipRects = ClipRects::create();
-  calculateClipRects(context, *clipRects);
-  return storeClipRectsInCache(context, parentClipRects, *clipRects);
+  ClipRects clipRects;
+  calculateClipRects(context, clipRects);
+  return storeClipRectsInCache(context, parentClipRects, clipRects);
 }
 
 void PaintLayerClipper::clearCache(ClipRectsCacheSlot cacheSlot) {
   if (cacheSlot == NumberOfClipRectsCacheSlots)
     m_layer.clearClipRectsCache();
   else if (ClipRectsCache* cache = m_layer.clipRectsCache())
     cache->clear(cacheSlot);
 }
 
 void PaintLayerClipper::clearClipRectsIncludingDescendants() {
@@ skipping 345 matching lines @@
     ClipRect testBackgroundClipRect =
         PaintLayerClipper(m_layer, nullptr).backgroundClipRect(context);
     CHECK_RECTS_EQ(testBackgroundClipRect, output);
 #endif
     return;
   }
   DCHECK(m_layer.parent());
   LayoutView* layoutView = m_layer.layoutObject().view();
   DCHECK(layoutView);
 
-  RefPtr<ClipRects> parentClipRects = ClipRects::create();
+  ClipRects parentClipRects;
   if (&m_layer == context.rootLayer) {
-    parentClipRects->reset(LayoutRect(LayoutRect::infiniteIntRect()));
+    parentClipRects.reset(LayoutRect(LayoutRect::infiniteIntRect()));
   } else {
     PaintLayerClipper(*m_layer.parent(), m_geometryMapper)
-        .getOrCalculateClipRects(context, *parentClipRects);
+        .getOrCalculateClipRects(context, parentClipRects);
   }
 
   output = backgroundClipRectForPosition(
-      *parentClipRects, m_layer.layoutObject().styleRef().position());
+      parentClipRects, m_layer.layoutObject().styleRef().position());
 
   // Note: infinite clipRects should not be scrolled here, otherwise they will
   // accidentally no longer be considered infinite.
-  if (parentClipRects->fixed() &&
+  if (parentClipRects.fixed() &&
       &context.rootLayer->layoutObject() == layoutView &&
       output != LayoutRect(LayoutRect::infiniteIntRect()))
     output.move(LayoutSize(layoutView->frameView()->getScrollOffset()));
 }
 
 void PaintLayerClipper::getOrCalculateClipRects(const ClipRectsContext& context,
                                                 ClipRects& clipRects) const {
   DCHECK(!m_geometryMapper);
 
   if (context.usesCache())
@@ skipping 36 matching lines @@
   DCHECK(!m_geometryMapper);
   ClipRectsContext context(rootLayer, PaintingClipRects,
                            IgnorePlatformOverlayScrollbarSize,
                            subpixelAccumulation);
   if (respectOverflowClip == IgnoreOverflowClip)
     context.setIgnoreOverflowClip();
   return getClipRects(context);
 }
 
 }  // namespace blink