Add "previewing on hover" support for single-field autocomplete input

components/autofill/content/common/autofill_messages.h

 // Copyright 2013 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.
 
 // Multiply-included message file, hence no include guard.
 
 #include <string>
 
 #include "base/time/time.h"
 #include "components/autofill/content/common/autofill_param_traits_macros.h"
@@ skipping 109 matching lines @@
 // Tells the renderer that the next form will be filled as a preview.
 IPC_MESSAGE_ROUTED0(AutofillMsg_SetAutofillActionPreview)
 
 // Tells the renderer that the Autofill previewed form should be cleared.
 IPC_MESSAGE_ROUTED0(AutofillMsg_ClearPreviewedForm)
 
 // Sets the currently selected node's value.
 IPC_MESSAGE_ROUTED1(AutofillMsg_SetNodeText,
                     base::string16 /* new node text */)
 
+// Sets preview suggested value for Autocomplete node
+IPC_MESSAGE_ROUTED1(AutofillMsg_PreviewAutoCompleteNode,

[Ilya Sherman, 2014/02/22 05:59:51]

Again, let's try to have parallel names and documentation for this message and
the one above it.  I'd suggest "AutofillMsg_FillFieldWithValue" and
"AutofillMsg_PreviewFieldWithValue", or maybe  "AutofillMsg_FillFormField" and
"AutofillMsg_PreviewFormField", or even just AutofillMsg_FillField" and
"AutofillMsg_PreviewField".  Feel free to brainstorm other names as well if you
prefer.

[ziran.sun, 2014/02/27 15:38:11]

Done.

[ziran.sun, 2014/02/27 15:38:11]

Done.

+                    base::string16 /* preview text */)

[Ilya Sherman, 2014/02/22 05:59:51]

nit: The commented out part is meant to be a variable name, so "preview text" ->
"value".  Please also fix line 128 while you're here.  Thanks :)

[ziran.sun, 2014/02/27 15:38:11]

Done.

+
 // Sets the currently selected node's value to be the given data list value.
 IPC_MESSAGE_ROUTED1(AutofillMsg_AcceptDataListSuggestion,
                     base::string16 /* accepted data list value */)
 
 // Tells the renderer to populate the correct password fields with this
 // generated password.
 IPC_MESSAGE_ROUTED1(AutofillMsg_GeneratedPasswordAccepted,
                     base::string16 /* generated_password */)
 
 // Tells the renderer that the password field has accept the suggestion.
@@ skipping 118 matching lines @@
 IPC_MESSAGE_ROUTED4(AutofillHostMsg_ShowPasswordSuggestions,
                     autofill::FormFieldData /* the form field */,
                     gfx::RectF /* input field bounds, window-relative */,
                     std::vector<base::string16> /* suggestions */,
                     std::vector<base::string16> /* realms */)
 
 // Inform browser of data list values for the curent field.
 IPC_MESSAGE_ROUTED2(AutofillHostMsg_SetDataList,
                     std::vector<base::string16> /* values */,
                     std::vector<base::string16> /* labels */)