Update SkPicture cull rects with RTree information

src/core/SkRTree.h

Index: src/core/SkRTree.h
diff --git a/src/core/SkRTree.h b/src/core/SkRTree.h
index 320b0bd438e8f627a71f01435d69846ed9e1de6e..9a118d4897b54a1bbd7788c814181fae31236526 100644
--- a/src/core/SkRTree.h
+++ b/src/core/SkRTree.h
@@ -52,6 +52,9 @@ public:
     // Insertion count (not overall node count, which may be greater).
     int getCount() const { return fCount; }
 
+    // Get the root bound.
+    SkRect getRootBound() const SK_OVERRIDE;
+
     // These values were empirically determined to produce reasonable performance in most cases.
     static const int kMinChildren = 6,
                      kMaxChildren = 11;