Implement convertToBlob() in OffscreenCanvas

third_party/WebKit/Source/core/html/canvas/CanvasAsyncBlobCreator.h

Index: third_party/WebKit/Source/core/html/canvas/CanvasAsyncBlobCreator.h
diff --git a/third_party/WebKit/Source/core/html/canvas/CanvasAsyncBlobCreator.h b/third_party/WebKit/Source/core/html/canvas/CanvasAsyncBlobCreator.h
index 178a267f26468c7b492235b1cf632cfe44d4cc1a..d5689df24149ded6badcbd48636c0f43723d331e 100644
--- a/third_party/WebKit/Source/core/html/canvas/CanvasAsyncBlobCreator.h
+++ b/third_party/WebKit/Source/core/html/canvas/CanvasAsyncBlobCreator.h
@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+#include "bindings/core/v8/ScriptPromiseResolver.h"
 #include "core/CoreExport.h"
 #include "core/dom/DOMTypedArray.h"
 #include "core/fileapi/BlobCallback.h"
@@ -28,9 +29,9 @@ class CORE_EXPORT CanvasAsyncBlobCreator
       const IntSize&,
       BlobCallback*,
       double,
-      Document&);
-  void scheduleAsyncBlobCreation(bool canUseIdlePeriodScheduling,
-                                 const double& quality = 0.0);
+      Document*,
+      ScriptPromiseResolver*);
+  void scheduleAsyncBlobCreation(const double& quality);
   virtual ~CanvasAsyncBlobCreator();
   enum MimeType {
     MimeTypePng,
@@ -50,6 +51,13 @@ class CORE_EXPORT CanvasAsyncBlobCreator
                            // types
     IdleTaskCount,         // Should not be seen in production
   };
+
+  enum ToBlobFunctionType {
+    HTMLCanvasToBlobCallback,
+    OffscreenCanvasToBlobPromise,
+    NumberOfToBlobFunctionTypes
+  };
+
   // Methods are virtual for mocking in unit tests
   virtual void signalTaskSwitchInStartTimeoutEventForTesting() {}
   virtual void signalTaskSwitchInCompleteTimeoutEventForTesting() {}
@@ -62,7 +70,8 @@ class CORE_EXPORT CanvasAsyncBlobCreator
                          const IntSize&,
                          BlobCallback*,
                          double,
-                         Document&);
+                         Document*,
+                         ScriptPromiseResolver*);
   // Methods are virtual for unit testing
   virtual void scheduleInitiatePngEncoding();
   virtual void scheduleInitiateJpegEncoding(const double&);
@@ -72,8 +81,8 @@ class CORE_EXPORT CanvasAsyncBlobCreator
                                            std::unique_ptr<WTF::Closure>,
                                            double delayMs);
   virtual void signalAlternativeCodePathFinishedForTesting() {}
-  virtual void createBlobAndInvokeCallback();
-  virtual void createNullAndInvokeCallback();
+  virtual void createBlobAndReturnResult();
+  virtual void createNullAndReturnResult();
 
   void initiatePngEncoding(double deadlineSeconds);
   void initiateJpegEncoding(const double& quality, double deadlineSeconds);
@@ -94,12 +103,19 @@ class CORE_EXPORT CanvasAsyncBlobCreator
   const IntSize m_size;
   size_t m_pixelRowStride;
   const MimeType m_mimeType;
-  Member<BlobCallback> m_callback;
   double m_startTime;
   double m_scheduleInitiateStartTime;
   double m_elapsedTime;
+
+  ToBlobFunctionType m_functionType;

[Justin Novosad, 2016/10/19 19:59:33]

This additional state is not necessary, you could just have this: 
bool usingPromise() {
  DCHECK(!m_callback ^ !m_scriptPromiseResolver);
  DCHECK(!m_document == !m_callback);
  return m_scriptPromiseResolver;
}

[xlai (Olivia), 2016/10/20 15:58:54]

I think this additional state is necessary for the UMA histogram. It needs
to distinguish between canvas.toBlob and OffscreenCanvas.convertToBlob with
an explicit enum type.

And also for the unit test.

+
+  // Used for HTMLCanvasElement only
+  Member<BlobCallback> m_callback;
   Member<ParentFrameTaskRunners> m_parentFrameTaskRunner;
 
+  // Used for OffscreenCanvas only
+  Member<ScriptPromiseResolver> m_scriptPromiseResolver;
+
   // PNG
   bool initializePngStruct();
   void