Make peekPixels() usable with raster surface snapshots

src/image/SkSurface_Raster.cpp

Index: src/image/SkSurface_Raster.cpp
diff --git a/src/image/SkSurface_Raster.cpp b/src/image/SkSurface_Raster.cpp
index d66aed213aeff1f05f1f8ae1a28c09d286635707..d59aef7c753228e885be6cc0516b530246b655eb 100644
--- a/src/image/SkSurface_Raster.cpp
+++ b/src/image/SkSurface_Raster.cpp
@@ -118,7 +118,10 @@ void SkSurface_Raster::onDraw(SkCanvas* canvas, SkScalar x, SkScalar y,
 }
 
 SkImage* SkSurface_Raster::onNewImageSnapshot(Budgeted) {
-    return SkNewImageFromRasterBitmap(fBitmap, fWeOwnThePixels, &this->props());
+    // Our pixels are in memory, so read access on the snapshot SkImage could be cheap.
+    // Lock the shared pixel ref to ensure peekPixels() is usable.
+    return SkNewImageFromRasterBitmap(fBitmap, fWeOwnThePixels, &this->props(),
+                                      kLocked_SharedPixelRefMode);
 }
 
 void SkSurface_Raster::onCopyOnWrite(ContentChangeMode mode) {