add peekPixels to canvas

src/core/SkDevice.cpp

 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkDevice.h"
 #include "SkMetaData.h"
 
@@ skipping 47 matching lines @@
 
 SkMetaData& SkBaseDevice::getMetaData() {
     // metadata users are rare, so we lazily allocate it. If that changes we
     // can decide to just make it a field in the device (rather than a ptr)
     if (NULL == fMetaData) {
         fMetaData = new SkMetaData;
     }
     return *fMetaData;
 }
 
+// TODO: when we can remove width/height/config from SkBaseDevice, then other
+// classes should explicitly override this guy.
+SkImageInfo SkBaseDevice::imageInfo() const {
+    return SkImageInfo::Make(this->width(),
+                             this->height(),
+                             SkBitmapConfigToColorType(this->config()),
+                             this->isOpaque() ? kOpaque_SkAlphaType :
+                                                kPremul_SkAlphaType);
+}
+
 const SkBitmap& SkBaseDevice::accessBitmap(bool changePixels) {
     const SkBitmap& bitmap = this->onAccessBitmap();
     if (changePixels) {
         bitmap.notifyPixelsChanged();
     }
     return bitmap;
 }
 
 bool SkBaseDevice::readPixels(SkBitmap* bitmap, int x, int y,
                               SkCanvas::Config8888 config8888) {
@@ skipping 32 matching lines @@
                                      srcRect.fLeft,
                                      srcRect.fTop,
                                      config8888);
     if (result && bmp == &tmp) {
         tmp.swap(*bitmap);
     }
     return result;
 }
 
 SkSurface* SkBaseDevice::newSurface(const SkImageInfo&) { return NULL; }
+
+const void* SkBaseDevice::peekPixels(SkImageInfo*, size_t*) { return NULL; }