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

components/autofill/content/renderer/autofill_agent.h

Index: components/autofill/content/renderer/autofill_agent.h
diff --git a/components/autofill/content/renderer/autofill_agent.h b/components/autofill/content/renderer/autofill_agent.h
index cb4df0317f580c4c423bf3eae2749a7278ddb4e1..a26c36b5f83916e9d027ca03b3e12118b44ce334 100644
--- a/components/autofill/content/renderer/autofill_agent.h
+++ b/components/autofill/content/renderer/autofill_agent.h
@@ -105,6 +105,7 @@ class AutofillAgent : public content::RenderViewObserver,
   void OnClearForm();
   void OnSetAutofillActionPreview();
   void OnClearPreviewedForm();
+  void OnPreviewAutoCompleteNode(const base::string16& value);

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

nit: Please move this to be right after "OnSetNodeText"

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

Done.

   void OnSetNodeText(const base::string16& value);
   void OnAcceptDataListSuggestion(const base::string16& value);
   void OnAcceptPasswordAutofillSuggestion(const base::string16& username);
@@ -173,6 +174,10 @@ class AutofillAgent : public content::RenderViewObserver,
   // Set |node| to display the given |value|.
   void SetNodeText(const base::string16& value, blink::WebInputElement* node);
 
+  // Set preview value for AutoComplete |node|.

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

nit: "Set |node| to display the given |value| as a preview.  The preview is
visible on screen to the user, but not visible to the page via the DOM or
JavaScript."

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

Done.

+  void PreviewAutoCompleteNode(const base::string16& value,
+                               blink::WebInputElement* node);
+
   // Hides any currently showing Autofill UI.
   void HideAutofillUI();