[Autofill] Migrate ContentAutofillDriver<-->AutofillAgent IPCs to mojo.

components/autofill/content/public/interfaces/autofill_agent.mojom

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 module autofill.mojom;
 
+import "components/autofill/content/public/interfaces/autofill_types.mojom";
+
 interface AutofillAgent {
   // Tells the render frame that a user gesture was observed
   // somewhere in the tab (including in a different frame).
   FirstUserGestureObservedInTab();
+
+  // Instructs the renderer to fill the active form with the given form data,
+  // the response contains filled form and the timestamp.
+  FillForm(int32 id, FormData form) => (FormData filled, int64 timestamp);

[yzshen1, 2016/05/24 16:12:10]

what is the exact meaning of the timestamp?

[leonhsl(Using Gerrit), 2016/05/25 07:16:34]

This is the timestamp when AutofillAgent received FillForm call and filled the
formdata. Originally it is carried in the response message as bellow:
IPC_MESSAGE_ROUTED2(AutofillHostMsg_DidFillAutofillFormData,
                    autofill::FormData /* the form */,
                    base::TimeTicks /* timestamp */) 

 };