Add autofill preview support for <month> input fields

Source/core/html/forms/BaseMultipleFieldsDateAndTimeInputType.cpp

 /*
  * Copyright (C) 2010 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 485 matching lines @@
 
 void BaseMultipleFieldsDateAndTimeInputType::updateView()
 {
     DateTimeEditElement* edit = dateTimeEditElement();
     if (!edit)
         return;
 
     DateTimeEditElement::LayoutParameters layoutParameters(element().locale(), createStepRange(AnyIsDefaultStep));
 
     DateComponents date;
-    const bool hasValue = parseToDateComponents(element().value(), &date);
+    bool hasValue = false;
+    if (!element().suggestedValue().isNull())
+        hasValue = parseToDateComponents(element().suggestedValue(), &date);
+    else if (!element().formControlValueMatchesRenderer())

[Ilya Sherman, 2014/02/08 01:22:18]

Why is it relevant whether the form control's value matches the renderer?  I
don't see this check having been needed before, so this is a pretty surprising
addition.

[ziran.sun, 2014/02/10 18:21:09]

Done.

[ziran.sun, 2014/02/10 18:21:09]

I noticed this check in updateView() in TextFieldInputType.cpp. It probably
doesn't make sense here I guess. I've removed this check. 

+        hasValue = parseToDateComponents(element().value(), &date);
     if (!hasValue)
         setMillisecondToDateComponents(layoutParameters.stepRange.minimum().toDouble(), &date);
 
     setupLayoutParameters(layoutParameters, date);
 
     const AtomicString pattern = edit->fastGetAttribute(HTMLNames::patternAttr);
     if (!pattern.isEmpty())
         layoutParameters.dateTimeFormat = pattern;
 
     if (!DateTimeFormatValidator().validateFormat(layoutParameters.dateTimeFormat, *this))
@@ skipping 85 matching lines @@
         clearButton->setInlineStyleProperty(CSSPropertyPointerEvents, CSSValueNone);
     } else {
         clearButton->removeInlineStyleProperty(CSSPropertyOpacity);
         clearButton->removeInlineStyleProperty(CSSPropertyPointerEvents);
     }
 }
 
 } // namespace WebCore
 
 #endif