Implement "Save image as" for canvas (blink side).

Source/core/html/HTMLCanvasElement.cpp

 /*
  * Copyright (C) 2004, 2006, 2007 Apple Inc. All rights reserved.
  * Copyright (C) 2007 Alp Toker <alp@atoker.com>
  * Copyright (C) 2010 Torch Mobile (Beijing) Co. Ltd. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
@@ skipping 365 matching lines @@
 {
     String lowercaseMimeType = mimeType.lower();
 
     // FIXME: Make isSupportedImageMIMETypeForEncoding threadsafe (to allow this method to be used on a worker thread).
     if (mimeType.isNull() || !MIMETypeRegistry::isSupportedImageMIMETypeForEncoding(lowercaseMimeType))
         lowercaseMimeType = "image/png";
 
     return lowercaseMimeType;
 }
 
-String HTMLCanvasElement::toDataURL(const String& mimeType, const double* quality, ExceptionState& exceptionState)
+const AtomicString HTMLCanvasElement::imageSourceURL() const
 {
-    if (!m_originClean) {
-        exceptionState.throwSecurityError("Tainted canvases may not be exported.");
-        return String();
-    }
+    return AtomicString(toDataURLInternal("image/png", 0));
+}
 
+String HTMLCanvasElement::toDataURLInternal(const String& mimeType, const double* quality) const
+{
     if (m_size.isEmpty() || !buffer())
         return String("data:,");
 
     String encodingMimeType = toEncodingMimeType(mimeType);
 
     // Try to get ImageData first, as that may avoid lossy conversions.
     RefPtrWillBeRawPtr<ImageData> imageData = getImageData();
 
     if (imageData)
         return ImageDataToDataURL(ImageDataBuffer(imageData->size(), imageData->data()), encodingMimeType, quality);
 
     if (m_context)
         m_context->paintRenderingResultsToCanvas();
 
     return buffer()->toDataURL(encodingMimeType, quality);
 }
 
-PassRefPtrWillBeRawPtr<ImageData> HTMLCanvasElement::getImageData()
+String HTMLCanvasElement::toDataURL(const String& mimeType, const double* quality, ExceptionState& exceptionState) const
+{
+    if (!m_originClean) {
+        exceptionState.throwSecurityError("Tainted canvases may not be exported.");
+        return String();
+    }
+
+    return toDataURLInternal(mimeType, quality);
+}
+
+PassRefPtrWillBeRawPtr<ImageData> HTMLCanvasElement::getImageData() const
 {
     if (!m_context || !m_context->is3d())
         return nullptr;
     return toWebGLRenderingContext(m_context.get())->paintRenderingResultsToImageData();
 }
 
 SecurityOrigin* HTMLCanvasElement::securityOrigin() const
 {
     return document().securityOrigin();
 }
@@ skipping 275 matching lines @@
 {
     return !originClean();
 }
 
 FloatSize HTMLCanvasElement::sourceSize() const
 {
     return FloatSize(width(), height());
 }
 
 }