Move download messages from Renderer to Frame filter.

content/common/frame_messages.h

Index: content/common/frame_messages.h
diff --git a/content/common/frame_messages.h b/content/common/frame_messages.h
index e514f2d3f560c1809f14992889077174644639d6..abce29da34f78b0c49034e03a1d289fdcbabccbf 100644
--- a/content/common/frame_messages.h
+++ b/content/common/frame_messages.h
@@ -879,6 +879,18 @@ IPC_MESSAGE_ROUTED3(FrameMsg_Find,
 // window (and what action to take regarding the selection).
 IPC_MESSAGE_ROUTED1(FrameMsg_StopFinding, content::StopFindAction /* action */)
 
+// Copies the image at location x, y to the clipboard (if there indeed is an
+// image at that location).
+IPC_MESSAGE_ROUTED2(FrameMsg_CopyImageAt,
+                    int /* x */,
+                    int /* y */)
+
+// Saves the image at location x, y to the disk (if there indeed is an
+// image at that location).
+IPC_MESSAGE_ROUTED2(FrameMsg_SaveImageAt,
+                    int /* x */,
+                    int /* y */)
+
 #if defined(ENABLE_PLUGINS)
 // Notifies the renderer of updates to the Plugin Power Saver origin whitelist.
 IPC_MESSAGE_ROUTED1(FrameMsg_UpdatePluginContentOriginWhitelist,
@@ -991,6 +1003,22 @@ IPC_MESSAGE_ROUTED1(FrameHostMsg_OpenURL, FrameHostMsg_OpenURL_Params)
 IPC_MESSAGE_ROUTED1(FrameHostMsg_DidFinishLoad,
                     GURL /* validated_url */)
 
+// Initiates a download based on user actions like 'ALT+click'.
+IPC_MESSAGE_CONTROL5(FrameHostMsg_DownloadUrl,

[asanka, 2016/05/18 16:26:54]

Shall we switch these two messages to ROUTED and skip the IDs?

[brettw, 2016/05/25 19:10:20]

This message isn't actually routed to the view. It's grabbed by the filter on
the I/O thread that then needs the parameters. If we changed it to be routed we
would need to use a lower-level message dispatch so the message handlers can get
the view IDs out. This would be more complicated.

+                     int /* render_view_id */,
+                     int /* render_frame_id */,
+                     GURL /* url */,
+                     content::Referrer /* referrer */,
+                     base::string16 /* suggested_name */)
+
+// Asks the browser to save a image (for <canvas> or <img>) from a data URL.
+// Note: |data_url| is the contents of a data:URL, and that it's represented as
+// a string only to work around size limitations for GURLs in IPC messages.
+IPC_MESSAGE_CONTROL3(FrameHostMsg_SaveImageFromDataURL,
+                     int /* render_view_id */,
+                     int /* render_frame_id */,
+                     std::string /* data_url */)
+
 // Sent when after the onload handler has been invoked for the document
 // in this frame. Sent for top-level frames. |report_type| and |ui_timestamp|
 // are used to report navigation metrics starting on the ui input event that