add peekPixels to SkCanvas and SkSurface

src/image/SkSurface.cpp

Index: src/image/SkSurface.cpp
diff --git a/src/image/SkSurface.cpp b/src/image/SkSurface.cpp
index cb029c8aea3b0e2672d1c840a35eb419a50c31e8..4b5fb68134bee8abe54385feb7ad16cf828aee25 100644
--- a/src/image/SkSurface.cpp
+++ b/src/image/SkSurface.cpp
@@ -121,3 +121,8 @@ void SkSurface::draw(SkCanvas* canvas, SkScalar x, SkScalar y,
                      const SkPaint* paint) {
     return asSB(this)->onDraw(canvas, x, y, paint);
 }
+
+const void* SkSurface::peekPixels(SkImageInfo* info, size_t* rowBytes) {
+    return this->getCanvas()->peekPixels(info, rowBytes);
+}
+