Track performance of toBlob and its complete timeout delay

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 64152fb3c0a5e14841d3073b9220150604079942..a2e9bb3535c15fd3eb54699b42d220517818fb46 100644
--- a/third_party/WebKit/Source/core/html/canvas/CanvasAsyncBlobCreator.h
+++ b/third_party/WebKit/Source/core/html/canvas/CanvasAsyncBlobCreator.h
@@ -35,6 +35,12 @@ public:
         IdleTaskSwitchedToMainThreadTask,
         IdleTaskNotSupported // Idle tasks are not implemented for some image types
     };
+    // enum used histogram
+    enum IdleTaskTimeoutType {
+        IdleTaskStartTimeout,
+        IdleTaskCompleteTimeout,
+        IdleTaskTimeoutSupported
+    };
     // Methods are virtual for mocking in unit tests
     virtual void signalTaskSwitchInStartTimeoutEventForTesting() { }
     virtual void signalTaskSwitchInCompleteTimeoutEventForTesting() { }
@@ -73,6 +79,8 @@ private:
     size_t m_pixelRowStride;
     const MimeType m_mimeType;
     CrossThreadPersistent<BlobCallback> m_callback;
+    double m_startTime;
+    void recordTimeoutEvent(IdleTaskTimeoutType);
 
     // PNG
     bool initializePngStruct();
@@ -85,8 +93,8 @@ private:
     // WEBP
     void encodeImageOnEncoderThread(double quality);
 
-    void idleTaskStartTimeoutEvent(double quality);
-    void idleTaskCompleteTimeoutEvent();
+    void idleTaskStartTimeoutEvent(double quality, double startTime);
+    void idleTaskCompleteTimeoutEvent(double startTime);
 };
 
 } // namespace blink