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 9f4002c7c4470e154b0603228d012ade0e9daa60..ad35d5827153012948bb4515c7b90c1fc7e10d16 100644
--- a/content/browser/renderer_host/render_view_host_impl.cc
+++ b/content/browser/renderer_host/render_view_host_impl.cc
@@ -1585,6 +1585,10 @@ 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));