Update SkPicture cull rects with RTree information

src/core/SkRTree.cpp

 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkRTree.h"
 
 SkRTree::SkRTree(SkScalar aspectRatio) : fCount(0), fAspectRatio(aspectRatio) {}
 
+SkRect SkRTree::getRootBound() const {
+    if (fCount) {
+        return fRoot.fBounds;
+    } else {
+        return SkRect::MakeEmpty();
+    }
+}
+
 void SkRTree::insert(const SkRect boundsArray[], int N) {
     SkASSERT(0 == fCount);
 
     SkTDArray<Branch> branches;
     branches.setReserve(N);
 
     for (int i = 0; i < N; i++) {
         const SkRect& bounds = boundsArray[i];
         if (bounds.isEmpty()) {
             continue;
@@ skipping 149 matching lines @@
     }
 }
 
 size_t SkRTree::bytesUsed() const {
     size_t byteCount = sizeof(SkRTree);
 
     byteCount += fNodes.reserved() * sizeof(Node);
 
     return byteCount;
 }