Deal gracefully with null {GraphicsContext,SkPictureBuilder}.endRecording() results.

third_party/WebKit/Source/platform/graphics/GraphicsContext.h

Index: third_party/WebKit/Source/platform/graphics/GraphicsContext.h
diff --git a/third_party/WebKit/Source/platform/graphics/GraphicsContext.h b/third_party/WebKit/Source/platform/graphics/GraphicsContext.h
index 1cf648d8dad969a124dbf56a26af869171d70246..7d7c3f6362fa33065162d7c0626a7353508c56a6 100644
--- a/third_party/WebKit/Source/platform/graphics/GraphicsContext.h
+++ b/third_party/WebKit/Source/platform/graphics/GraphicsContext.h
@@ -211,6 +211,8 @@ public:
     // are stored in a display list that can be replayed at a later time. Pass in the bounding
     // rectangle for the content in the list.
     void beginRecording(const FloatRect&);
+    // Returns a picture with any recorded draw commands since the prerequisite call to beginRecording(),
+    // or nullptr if the canvas is disabled.

[chrishtr, 2016/03/29 22:42:23]

add the second sentence

[wkorman, 2016/03/29 22:52:02]

Done, more specific phrasing here since this is the source of it all, as it
were.

     PassRefPtr<SkPicture> endRecording();
 
     void setShadow(const FloatSize& offset, float blur, const Color&,