add peekPixels to canvas

src/core/SkBitmapDevice.cpp

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkBitmapDevice.h"
 #include "SkConfig8888.h"
 #include "SkDraw.h"
@@ skipping 368 matching lines @@
 void SkBitmapDevice::drawDevice(const SkDraw& draw, SkBaseDevice* device,
                                 int x, int y, const SkPaint& paint) {
     const SkBitmap& src = device->accessBitmap(false);
     draw.drawSprite(src, x, y, paint);
 }
 
 SkSurface* SkBitmapDevice::newSurface(const SkImageInfo& info) {
     return SkSurface::NewRaster(info);
 }
 
+const void* SkBitmapDevice::peekPixels(SkImageInfo* info, size_t* rowBytes) {
+    if (fBitmap.getPixels() && fBitmap.asImageInfo(info)) {
+        if (rowBytes) {
+            *rowBytes = fBitmap.rowBytes();
+        }
+        return fBitmap.getPixels();
+    }
+    return NULL;
+}
+
 ///////////////////////////////////////////////////////////////////////////////
 
 bool SkBitmapDevice::filterTextFlags(const SkPaint& paint, TextFlags* flags) {
     if (!paint.isLCDRenderText() || !paint.isAntiAlias()) {
         // we're cool with the paint as is
         return false;
     }
 
     if (SkBitmap::kARGB_8888_Config != fBitmap.config() ||
         paint.getRasterizer() ||
         paint.getPathEffect() ||
         paint.isFakeBoldText() ||
         paint.getStyle() != SkPaint::kFill_Style ||
         !SkXfermode::IsMode(paint.getXfermode(), SkXfermode::kSrcOver_Mode)) {
         // turn off lcd
         flags->fFlags = paint.getFlags() & ~SkPaint::kLCDRenderText_Flag;
         flags->fHinting = paint.getHinting();
         return true;
     }
     // we're cool with the paint as is
     return false;
 }