Add text field change handling for autofill preview in textarea element.

public/web/WebAutofillClient.h

Index: public/web/WebAutofillClient.h
diff --git a/public/web/WebAutofillClient.h b/public/web/WebAutofillClient.h
index bb808083cb955f9b8995b5d968dc776794ea0441..ae33b33f6570b584c61bb51b6ed6cc6260572833 100644
--- a/public/web/WebAutofillClient.h
+++ b/public/web/WebAutofillClient.h
@@ -33,6 +33,7 @@
 
 namespace blink {
 
+class WebFormControlElement;
 class WebFormElement;
 class WebFrame;
 class WebInputElement;
@@ -58,7 +59,7 @@ public:
 
     // These methods are called when the users edits a text-field.
     virtual void textFieldDidEndEditing(const WebInputElement&) { }
-    virtual void textFieldDidChange(const WebInputElement&) { }
+    virtual void textFieldDidChange(const WebFormControlElement&) { }

[tkent, 2014/02/06 00:05:45]

Is the WebAutofillClient implementation in Chromium ready for this change?
If this CL is landed and the WebAutofillClient still implements the old
signature, the WebAutofillClient doesn't receive textFieldDidChange
notification.

[ziran.sun, 2014/02/06 10:32:17]

Yes. Check line 93
https://codereview.chromium.org/140093005/diff/1/components/autofill/content/...

I guess this CL needs to land together with the CL in the link? I've added you
as reviewer for above commit. Hope it's okay.

[tkent, 2014/02/07 06:04:09]

It's almost impossible to land a Chromium CL and a Blink CL at the same time
because of Blink roll delay.

The process should be:
1. Chromium: Remove OVERRIDE from textFieldDidChange(const WebInputElement&),
and add textFieldDidChange(const WebFormControlElement&) implementation without
OVERRIDE.
2. Blink: Land this CL
3. Wait until next Blink roll
4. Chromium: Remove textFieldDidChange(const WebInputElement&), and add OVERRIDE
to textFieldDidChange(const WebFormControlElement&)

     virtual void textFieldDidReceiveKeyDown(const WebInputElement&, const WebKeyboardEvent&) { }
     // This is called when a datalist indicator is clicked.
     virtual void openTextDataListChooser(const WebInputElement&) { }