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

content/browser/renderer_host/render_view_host_impl.cc

Index: content/browser/renderer_host/render_view_host_impl.cc
diff --git a/content/browser/renderer_host/render_view_host_impl.cc b/content/browser/renderer_host/render_view_host_impl.cc
index 878ae78adbfbf7e03b9339ea7df1f7a87ab85948..70695137863b98d33e8249c5869ba0cf2b5bfd09 100644
--- a/content/browser/renderer_host/render_view_host_impl.cc
+++ b/content/browser/renderer_host/render_view_host_impl.cc
@@ -1577,6 +1577,10 @@ void RenderViewHostImpl::CopyImageAt(int x, int y) {
   Send(new ViewMsg_CopyImageAt(GetRoutingID(), x, y));
 }
 
+void RenderViewHostImpl::SaveImageAt(int x, int y) {
+  Send(new ViewMsg_SaveImageAt(GetRoutingID(), x, y));
+}
+
 void RenderViewHostImpl::ExecuteMediaPlayerActionAtLocation(
   const gfx::Point& location, const blink::WebMediaPlayerAction& action) {
   Send(new ViewMsg_MediaPlayerActionAt(GetRoutingID(), location, action));