Add SkBBoxHierarchy::reserve() as an optional size hint.

src/core/SkBBoxHierarchy.h

 
 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkBBoxHierarchy_DEFINED
 #define SkBBoxHierarchy_DEFINED
 
 #include "SkRect.h"
 #include "SkTDArray.h"
 #include "SkRefCnt.h"
 
 /**
  * Interface for a spatial data structure that associates user data with axis-aligned
  * bounding boxes, and allows efficient retrieval of intersections with query rectangles.
  */
 class SkBBoxHierarchy : public SkRefCnt {
 public:
     SK_DECLARE_INST_COUNT(SkBBoxHierarchy)
 
     SkBBoxHierarchy() {}
 
     /**
-     * Insert opIndex and corresponding bounding box
+     * Hint that <= opCount calls to insert() will be made.
+     */
+    virtual void reserve(unsigned opCount) {}
+
+    /**
+     * Insert opIndex and corresponding bounding box.
      * @param opIndex Any value, will be returned in order.
-     * @param bounds The bounding box, should not be empty
+     * @param bounds The bounding box, should not be empty.
      * @param defer Whether or not it is acceptable to delay insertion of this element (building up
      *        an entire spatial data structure at once is often faster and produces better
      *        structures than repeated inserts) until flushDeferredInserts is called or the first
      *        search.
      */
     virtual void insert(unsigned opIndex, const SkRect& bounds, bool defer = false) = 0;
 
     /**
-     * If any insertions have been deferred, this forces them to be inserted
+     * If any insertions have been deferred, force them to be inserted.
      */
-    virtual void flushDeferredInserts() = 0;
+    virtual void flushDeferredInserts() {}
 
     /**
      * Populate results with sorted opIndex corresponding to bounding boxes that intersect query.
      */
     virtual void search(const SkRect& query, SkTDArray<unsigned>* results) const = 0;
 
 private:
     typedef SkRefCnt INHERITED;
 };
 
 #endif