Fix a minor issue in OffscreenCanvas.drawImage

third_party/WebKit/Source/core/offscreencanvas/OffscreenCanvas.cpp

Index: third_party/WebKit/Source/core/offscreencanvas/OffscreenCanvas.cpp
diff --git a/third_party/WebKit/Source/core/offscreencanvas/OffscreenCanvas.cpp b/third_party/WebKit/Source/core/offscreencanvas/OffscreenCanvas.cpp
index 7509d86c81e6e5077057d91abf0426c203f29d31..9dc16fe3792d4b26a1c98ef6d5cd7be7dc1425b0 100644
--- a/third_party/WebKit/Source/core/offscreencanvas/OffscreenCanvas.cpp
+++ b/third_party/WebKit/Source/core/offscreencanvas/OffscreenCanvas.cpp
@@ -93,7 +93,10 @@ PassRefPtr<Image> OffscreenCanvas::getSourceImageForCanvas(
     const FloatSize& size) const {
   if (!m_context) {
     *status = InvalidSourceImageStatus;
-    return nullptr;
+    sk_sp<SkSurface> surface =
+        SkSurface::MakeRasterN32Premul(m_size.width(), m_size.height());
+    return surface ? StaticBitmapImage::create(surface->makeImageSnapshot())
+                   : nullptr;
   }
   if (!size.width() || !size.height()) {
     *status = ZeroSizeCanvasSourceImageStatus;