Reuse cc::PictureLayers when possible for SPv2.

third_party/WebKit/Source/platform/graphics/paint/PaintArtifact.cpp

 // 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.
 
 #include "platform/graphics/paint/PaintArtifact.h"
 
 #include "platform/TraceEvent.h"
 #include "platform/geometry/IntRect.h"
 #include "platform/graphics/GraphicsLayer.h"
 #include "platform/graphics/paint/DrawingDisplayItem.h"
 #include "public/platform/WebDisplayItemList.h"
 #include "third_party/skia/include/core/SkRegion.h"
 
 namespace blink {
 
 namespace {
 
 void computeChunkBoundsAndOpaqueness(const DisplayItemList& displayItems, Vector<PaintChunk>& paintChunks)
 {
     for (PaintChunk& chunk : paintChunks) {
         FloatRect bounds;
-        SkRegion knownToBeOpaqueRegion;
+        FloatRect knownToBeOpaqueRegion;
         for (const DisplayItem& item : displayItems.itemsInPaintChunk(chunk)) {
+            FloatRect visualRect(item.client().visualRect());
+
+            bounds.unite(visualRect);
             if (!item.isDrawing())
                 continue;
             const auto& drawing = static_cast<const DrawingDisplayItem&>(item);
             if (const SkPicture* picture = drawing.picture()) {
-                const SkRect& pictureRect = picture->cullRect();
-                bounds.unite(pictureRect);
                 if (drawing.knownToBeOpaque()) {

[Xianzhu, 2016/09/20 23:13:41]

There seems a problem: the picture may be smaller than the client's visual rect
(which covers all pictures of the client), so one picture is opaque doesn't mean
the whole client visual rect is opaque.

[chrishtr, 2016/09/20 23:43:59]

Good point. Reverted this part.

-                    // TODO(pdr): This may be too conservative and fail due to
-                    // floating point precision issues.
-                    SkIRect conservativelyRoundedPictureRect;
-                    pictureRect.roundIn(&conservativelyRoundedPictureRect);
-                    knownToBeOpaqueRegion.op(conservativelyRoundedPictureRect, SkRegion::kUnion_Op);
+                    // TODO(pdr): It may be too conservative to round in to the enclosedIntRect.
+                    knownToBeOpaqueRegion.unite(enclosedIntRect(visualRect));
                 }
             }
         }
         chunk.bounds = bounds;
         if (knownToBeOpaqueRegion.contains(enclosingIntRect(bounds)))
             chunk.knownToBeOpaque = true;
     }
 }
 
 } // namespace
@@ skipping 55 matching lines @@
     TRACE_EVENT0("blink,benchmark", "PaintArtifact::appendToWebDisplayItemList");
     size_t visualRectIndex = 0;
     for (const DisplayItem& displayItem : m_displayItemList) {
         displayItem.appendToWebDisplayItemList(m_displayItemList.visualRect(visualRectIndex), list);
         visualRectIndex++;
     }
     list->setIsSuitableForGpuRasterization(isSuitableForGpuRasterization());
 }
 
 } // namespace blink