make onReadPixels protected and have default impl (so we can remove chrome override)

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 172 matching lines @@
     SkASSERT(x + info.width() <= dstInfo.width());
     SkASSERT(y + info.height() <= dstInfo.height());
 #endif
     return this->onWritePixels(info, pixels, rowBytes, x, y);
 }
 
 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;
+}
+
 #ifdef SK_SUPPORT_LEGACY_WRITEPIXELSCONFIG
 void SkBaseDevice::writePixels(const SkBitmap&, int x, int y, SkCanvas::Config8888) {}
 #endif