change internals over to SkPixmap and stop using accessBitmap

BUG=skia:

Review URL: https://codereview.chromium.org/1155443004
diff --git a/src/core/SkPictureRecord.h b/src/core/SkPictureRecord.h
index 7a6fc81..af65013 100644
--- a/src/core/SkPictureRecord.h
+++ b/src/core/SkPictureRecord.h
@@ -147,9 +147,7 @@
     }
 
     SkSurface* onNewSurface(const SkImageInfo&, const SkSurfaceProps&) override;
-    const void* onPeekPixels(SkImageInfo*, size_t*) override {
-        return NULL;
-    }
+    bool onPeekPixels(SkPixmap*) override { return false; }
 
     void willSave() override;
     SaveLayerStrategy willSaveLayer(const SkRect*, const SkPaint*, SaveFlags) override;