add peekPixels to SkCanvas and SkSurface

src/core/SkPictureRecord.h

 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkPictureRecord_DEFINED
 #define SkPictureRecord_DEFINED
 
@@ skipping 203 matching lines @@
     void validateRegions() const;
 #else
 public:
     void validate(size_t initialOffset, uint32_t size) const {
         SkASSERT(fWriter.bytesWritten() == initialOffset + size);
     }
 #endif
 
 protected:
     virtual SkSurface* onNewSurface(const SkImageInfo&) SK_OVERRIDE;
+    const void* onPeekPixels(SkImageInfo*, size_t*) SK_OVERRIDE {
+        return NULL;
+    }
 
     // Return fontmetrics.fTop,fBottom in topbot[0,1], after they have been
     // tweaked by paint.computeFastBounds().
     static void ComputeFontMetricsTopBottom(const SkPaint& paint, SkScalar topbot[2]);
 
     // Make sure that flat has fTopBot written.
     static void WriteTopBot(const SkPaint& paint, const SkFlatData& flat) {
         if (!flat.isTopBotWritten()) {
             ComputeFontMetricsTopBottom(paint, flat.writableTopBot());
             SkASSERT(flat.isTopBotWritten());
@@ skipping 52 matching lines @@
     friend class SkPictureTester; // for unit testing
 
 #ifdef SK_COLLAPSE_MATRIX_CLIP_STATE
     SkMatrixClipStateMgr fMCMgr;
 #endif
 
     typedef SkCanvas INHERITED;
 };
 
 #endif