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

Source/web/WebViewImpl.cpp

 /*
  * Copyright (C) 2011, 2012 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 3166 matching lines @@
         // we actually tried to retreive the image.
         //
         // FIXME: implement a cache of the most recent HitTestResult to avoid having
         //        to do two hit tests.
         return;
     }
 
     m_page->mainFrame()->editor().copyImage(result);
 }
 
+void WebViewImpl::saveImageAt(const WebPoint& point)
+{
+    if (!m_page)
+        return;
+
+    KURL url = hitTestResultForWindowPos(point).absoluteImageURL();
+
+    if (url.isEmpty())
+        return;
+
+    ResourceRequest request(url);
+    m_page->mainFrame()->loader().client()->loadURLExternally(
+        request, NavigationPolicyDownloadTo, WebString());
+}
+
 void WebViewImpl::dragSourceEndedAt(
     const WebPoint& clientPoint,
     const WebPoint& screenPoint,
     WebDragOperation operation)
 {
     PlatformMouseEvent pme(clientPoint,
                            screenPoint,
                            LeftButton, PlatformEvent::MouseMoved, 0, false, false, false,
                            false, 0);
     m_page->mainFrame()->eventHandler().dragSourceEndedAt(pme,
@@ skipping 912 matching lines @@
     const PageScaleConstraints& constraints = m_pageScaleConstraintsSet.pageDefinedConstraints();
 
     if (!mainFrameImpl() || !mainFrameImpl()->frameView())
         return false;
 
     return mainFrameImpl()->frameView()->layoutSize().width() == m_size.width
         || (constraints.minimumScale == constraints.maximumScale && constraints.minimumScale != -1);
 }
 
 } // namespace blink