Support aria-grabbed attribute.

Source/modules/accessibility/AXObject.h

Index: Source/modules/accessibility/AXObject.h
diff --git a/Source/modules/accessibility/AXObject.h b/Source/modules/accessibility/AXObject.h
index b5e1e4a66b2077eabdea9c650d38f7d39148019c..123ee7145751a8e905da5c26bda19c1422d2cad7 100644
--- a/Source/modules/accessibility/AXObject.h
+++ b/Source/modules/accessibility/AXObject.h
@@ -261,6 +261,12 @@ enum AccessibilityExpanded {
     ExpandedExpanded,
 };
 
+enum AccessibilityDefined {

[dmazzoni, 2014/11/19 17:20:17]

The enum looks great but I'm not sure I like calling it "Defined", because
really it's a boolean true / false, that also supports being undefined.

How about:

enum AccessibilityOptionalBool {
    OptionalBoolUndefined = 0,
    OptionalBoolTrue = 1,
    OptionalBoolFalse = 2
}

[je_julie(Not used), 2014/11/20 02:37:43]

Good idea. 
I updated patchset with that.

+    DefinedUndefined = 0,
+    DefinedFalse,
+    DefinedTrue
+};
+
 class AXObject : public RefCounted<AXObject> {
 public:
     typedef Vector<RefPtr<AXObject> > AccessibilityChildrenVector;
@@ -448,7 +454,7 @@ public:
     bool ariaPressedIsPresent() const;
     virtual AccessibilityRole ariaRoleAttribute() const { return UnknownRole; }
     virtual bool ariaRoleHasPresentationalChildren() const { return false; }
-    virtual bool isARIAGrabbed() { return false; }
+    virtual AccessibilityDefined isAriaGrabbed() const { return DefinedUndefined; }
     virtual bool isPresentationalChildOfAriaRole() const { return false; }
     virtual bool shouldFocusActiveDescendant() const { return false; }
     bool supportsARIAAttributes() const;