support direct writing to top layer

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 176 matching lines @@
 }
 
 bool SkBaseDevice::onWritePixels(const SkImageInfo&, const void*, size_t, int, int) {
     return false;
 }
 
 bool SkBaseDevice::onReadPixels(const SkBitmap&, int x, int y, SkCanvas::Config8888) {
     return false;
 }
 
+void* SkBaseDevice::accessPixels(SkImageInfo* info, size_t* rowBytes) {
+    SkImageInfo tmpInfo;
+    size_t tmpRowBytes;
+    if (NULL == info) {
+        info = &tmpInfo;
+    }
+    if (NULL == rowBytes) {
+        rowBytes = &tmpRowBytes;
+    }
+    return this->onAccessPixels(info, rowBytes);
+}
+
+void* SkBaseDevice::onAccessPixels(SkImageInfo* info, size_t* rowBytes) {
+    return NULL;
+}
+
 #ifdef SK_SUPPORT_LEGACY_WRITEPIXELSCONFIG
 void SkBaseDevice::writePixels(const SkBitmap&, int x, int y, SkCanvas::Config8888) {}
 #endif