Reuse cc::PictureLayers when possible for SPv2.

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

Index: third_party/WebKit/Source/platform/graphics/paint/PaintArtifact.cpp
diff --git a/third_party/WebKit/Source/platform/graphics/paint/PaintArtifact.cpp b/third_party/WebKit/Source/platform/graphics/paint/PaintArtifact.cpp
index 528f31b886948436f746505e57ddf1a07b3a61bc..90bc1957900a56aa56f83b903ed3aa5583d77c07 100644
--- a/third_party/WebKit/Source/platform/graphics/paint/PaintArtifact.cpp
+++ b/third_party/WebKit/Source/platform/graphics/paint/PaintArtifact.cpp
@@ -19,20 +19,18 @@ void computeChunkBoundsAndOpaqueness(const DisplayItemList& displayItems, Vector
 {
     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));
                 }
             }
         }