[HTMLCanvasElement.toBlob] Default callback version without scheduler

Source/platform/graphics/ImageBuffer.h

Index: Source/platform/graphics/ImageBuffer.h
diff --git a/Source/platform/graphics/ImageBuffer.h b/Source/platform/graphics/ImageBuffer.h
index 9ebb5ee89e510f13373d4d2b7a469f9936842aff..ab15def7eda26bb871ff801fcb0b50a3dd635539 100644
--- a/Source/platform/graphics/ImageBuffer.h
+++ b/Source/platform/graphics/ImageBuffer.h
@@ -43,6 +43,8 @@
 #include "wtf/PassOwnPtr.h"
 #include "wtf/PassRefPtr.h"
 #include "wtf/Uint8ClampedArray.h"
+#include "wtf/Vector.h"
+#include "wtf/text/WTFString.h"
 
 namespace WTF {
 
@@ -145,7 +147,8 @@ private:
 
 struct ImageDataBuffer {
     ImageDataBuffer(const IntSize& size, unsigned char* data) : m_data(data), m_size(size) { }
-    String PLATFORM_EXPORT toDataURL(const String& mimeType, const double* quality) const;
+    String PLATFORM_EXPORT toDataURL(const String& mimeType, const double* quality);
+    bool PLATFORM_EXPORT encodeImage(const String& mimeType, const double* quality, Vector<char>* output);
     unsigned char* pixels() const { return m_data; }
     int height() const { return m_size.height(); }
     int width() const { return m_size.width(); }