Implement convertToBlob() in OffscreenCanvas

third_party/WebKit/Source/modules/offscreencanvas/OffscreenCanvasModules.h

Index: third_party/WebKit/Source/modules/offscreencanvas/OffscreenCanvasModules.h
diff --git a/third_party/WebKit/Source/modules/offscreencanvas/OffscreenCanvasModules.h b/third_party/WebKit/Source/modules/offscreencanvas/OffscreenCanvasModules.h
index 1f6fe3e8f160d820e407f182a2a8e98c855680e7..8c46c45346b301e7d3c4f9a242976937ce6228cb 100644
--- a/third_party/WebKit/Source/modules/offscreencanvas/OffscreenCanvasModules.h
+++ b/third_party/WebKit/Source/modules/offscreencanvas/OffscreenCanvasModules.h
@@ -26,6 +26,16 @@ class MODULES_EXPORT OffscreenCanvasModules {
                          const CanvasContextCreationAttributes&,
                          ExceptionState&,
                          OffscreenRenderingContext&);
+
+  static ScriptPromise convertToBlob(ScriptState*,
+                                     OffscreenCanvas&,
+                                     const ImageEncodeOptions&,
+                                     ExceptionState&);
+
+ private:
+  static ImageData* toImageData(OffscreenCanvas&,
+                                SourceDrawingBuffer,
+                                SnapshotReason);
 };
 
 }  // namespace blink