Add error return, upon mask creation failure, in sw_draw_with_mask_filter

Bug: 822680

Change-Id: I7296c5be4faf1f706ad1cc05198559771e324841
Reviewed-on: https://skia-review.googlesource.com/116180
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>
diff --git a/src/gpu/GrBlurUtils.cpp b/src/gpu/GrBlurUtils.cpp
index b37da26..cc59c02 100644
--- a/src/gpu/GrBlurUtils.cpp
+++ b/src/gpu/GrBlurUtils.cpp
@@ -92,12 +92,18 @@
     bm.setImmutable();
 
     sk_sp<SkImage> image = SkImage::MakeFromBitmap(bm);
+    if (!image) {
+        return false;
+    }
 
     auto proxyProvider = context->contextPriv().proxyProvider();
     sk_sp<GrTextureProxy> maskProxy = proxyProvider->createTextureProxy(std::move(image),
                                                                         kNone_GrSurfaceFlags,
                                                                         1, SkBudgeted::kYes,
                                                                         SkBackingFit::kApprox);
+    if (!maskProxy) {
+        return false;
+    }
 
     return draw_mask(renderTargetContext, clipData, viewMatrix,
                      dstM.fBounds, std::move(paint), std::move(maskProxy));