Add autofill preview support for <month> input fields

Source/core/html/forms/BaseMultipleFieldsDateAndTimeInputType.cpp

Index: Source/core/html/forms/BaseMultipleFieldsDateAndTimeInputType.cpp
diff --git a/Source/core/html/forms/BaseMultipleFieldsDateAndTimeInputType.cpp b/Source/core/html/forms/BaseMultipleFieldsDateAndTimeInputType.cpp
index 3fbe6236e7b4398297633f29013a9b138c182de6..dbf63d278550d8ca20a8d18e2a1fd1e9cd4fa217 100644
--- a/Source/core/html/forms/BaseMultipleFieldsDateAndTimeInputType.cpp
+++ b/Source/core/html/forms/BaseMultipleFieldsDateAndTimeInputType.cpp
@@ -503,7 +503,11 @@ void BaseMultipleFieldsDateAndTimeInputType::updateView()
     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);