Don't draw if SkShader::asNewFragmentProcessor fails.

BUG=chromium:473156

Review URL: https://codereview.chromium.org/1089063002
diff --git a/include/gpu/SkGr.h b/include/gpu/SkGr.h
index 026b256..c73701e 100644
--- a/include/gpu/SkGr.h
+++ b/include/gpu/SkGr.h
@@ -81,14 +81,14 @@
 // an optimization where the color filter can be applied to the SkPaint's
 // color once while converting to GrPaint and then ignored. TODO: Remove this
 // bool and use the invariant info to automatically apply the color filter.
-void SkPaint2GrPaintNoShader(GrContext* context, GrRenderTarget*, const SkPaint& skPaint,
+bool SkPaint2GrPaintNoShader(GrContext* context, GrRenderTarget*, const SkPaint& skPaint,
                              GrColor paintColor, bool constantColor, GrPaint* grPaint);
 
 // This function is similar to skPaint2GrPaintNoShader but also converts
 // skPaint's shader to a GrFragmentProcessor if possible.
 // constantColor has the same meaning as in skPaint2GrPaintNoShader.
-void SkPaint2GrPaintShader(GrContext* context, GrRenderTarget*, const SkPaint& skPaint,
-                           const SkMatrix& viewM, bool constantColor, GrPaint* grPaint);
+bool SkPaint2GrPaint(GrContext* context, GrRenderTarget*, const SkPaint& skPaint,
+                     const SkMatrix& viewM, bool constantColor, GrPaint* grPaint);
 
 ////////////////////////////////////////////////////////////////////////////////
 // Classes