Adding support for DOM3 KeyboardEvents Code in KeyboardEvents

Source/core/events/KeyboardEvent.idl

Index: Source/core/events/KeyboardEvent.idl
diff --git a/Source/core/events/KeyboardEvent.idl b/Source/core/events/KeyboardEvent.idl
index f789f02249d90366cd235ef6c7d29d5f2766061c..d8ec816e06a3a304fd355bff8b6cd3ff3cb42a8b 100644
--- a/Source/core/events/KeyboardEvent.idl
+++ b/Source/core/events/KeyboardEvent.idl
@@ -26,6 +26,7 @@
     const unsigned long DOM_KEY_LOCATION_RIGHT    = 0x02;
     const unsigned long DOM_KEY_LOCATION_NUMPAD   = 0x03;
 
+    readonly attribute DOMString                                        code;

[Rick Byers, 2015/01/20 14:49:56]

This should be initialized by the constructor as well (and there should be a
test that verifies it can be set with a constructor).

Please put your new API surface area behind a RuntimeEnabledFeature
(http://www.chromium.org/blink/runtime-enabled-features) that's initially
'experimental'.  Once all chromium/blink CLs have landed and some basic compat
testing has been done across platforms, we can switch it to 'Stable'.  Worst
case and we discover some compat breakage we can just flip it back to
'Experimental' (rather than have to revert your CLs) while we address issues.

[Habib Virji, 2015/01/22 16:01:30]

Are you refering to below initKeyboardEvent? My understanding is wez has
suggested to be removed, as this interface is obsolete. If refering to
KeyboardEvent() constructors, it does initialize code value, except for the one
initialized by initiKeyboardEvent.  

Have added this API changes in runtime enabled feature. 

     [InitializedByEventConstructor] readonly attribute DOMString        keyIdentifier;
     [InitializedByEventConstructor] readonly attribute unsigned long    location;
     [ImplementedAs=location, DeprecateAs=KeyboardEventKeyLocation, InitializedByEventConstructor] readonly attribute unsigned long keyLocation; // Deprecated.