Adding nullptr check in CanvasRenderingContext2D::draw

BUG=522799
NOTRY=true

Review URL: https://codereview.chromium.org/1288063010

git-svn-id: svn://svn.chromium.org/blink/trunk@200919 bbb929c8-8fbe-4397-9dbb-9b2b20218538

third_party/WebKit/Source/modules/canvas2d/CanvasRenderingContext2D.cpp

@@ -885,7 +885,7 @@ bool CanvasRenderingContext2D::draw(const DrawFunc& drawFunc, const ContainsFunc
         return false;
 
     SkIRect clipBounds;
-    if (!drawingCanvas()->getClipDeviceBounds(&clipBounds))
+    if (!drawingCanvas() || !drawingCanvas()->getClipDeviceBounds(&clipBounds))
         return false;
 
     // If gradient size is zero, then paint nothing.