Implement computedRole and computedName (behind a flag)

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 efaa8a6f0c50b4a9def0b351a6528d5e889cefe3..ad86e52f7d72f127f2d7fb4185bc834194ca2089 100644
--- a/Source/modules/accessibility/AXObject.h
+++ b/Source/modules/accessibility/AXObject.h
@@ -40,6 +40,7 @@
 namespace blink {
 
 class AXObject;
+class AXObjectCache;
 class AXObjectCacheImpl;
 class Element;
 class FrameView;
@@ -52,6 +53,7 @@ class Widget;
 typedef unsigned AXID;
 
 enum AccessibilityRole {
+    NoRole = 0,

[dmazzoni, 2014/12/09 00:49:51]

I still vote for reusing UnknownRole rather than introducing a new NoRole.

If you introduce NoRole, you'll have to add a WebAXRole and plumb it through to
Chromium code too.

[aboxhall, 2014/12/13 01:38:36]

Is that accurate? It seems to compile and run fine without it. Note that we're
never actually setting it as something's official role - it's a placeholder for
"this thing doesn't have any particular role".

It's also nice to have a zero value so that NumRoles accurately reflects the
number of roles.

[dmazzoni, 2014/12/16 19:18:19]

Switch statements on enums should always explicitly handle all cases - it's a
very important tool to catch bugs at compile time. The only reason we can't do
that now is because Blink is a separate repository. As soon as the repositories
merge I'm going to fix that.

Right now we have to manually ensure that all Blink role enums are handled by
Chromium. By introducing a role that Blink won't actually return, you're
imposing a cognitive load on anyone who's tracing through the code and trying to
figure out if we're handling all of the possible roles.
Yes, but how is that different than UnknownRole? It's just a different name for
the same thing.
Great, so you're welcome to move UnknownRole to the top of the list and set it
to value 0.

[aboxhall, 2014/12/16 23:56:37]

Done.

     AlertDialogRole = 1,
     AlertRole,
     AnnotationRole,
@@ -167,6 +169,7 @@ enum AccessibilityRole {
     UserInterfaceTooltipRole,
     WebAreaRole,
     WindowRole,
+    NumRoles
 };
 
 enum AccessibilityTextSource {
@@ -281,7 +284,7 @@ public:
     };
 
 protected:
-    AXObject();
+    AXObject(AXObjectCache*);
 
 public:
     virtual ~AXObject();
@@ -576,6 +579,7 @@ public:
     static bool isARIAInput(AccessibilityRole);
     static AccessibilityRole ariaRoleToWebCoreRole(const String&);
     static IntRect boundingBoxForQuads(RenderObject*, const Vector<FloatQuad>&);
+    static const AtomicString& roleName(const AccessibilityRole);
 
 protected:
     AXID m_id;
@@ -606,6 +610,8 @@ protected:
     mutable bool m_cachedIsIgnored;
     mutable const AXObject* m_cachedLiveRegionRoot;
 
+    AXObjectCacheImpl* m_axObjectCache;
+
     // Updates the cached attribute values. This may be recursive, so to prevent deadlocks,
     // functions called here may only search up the tree (ancestors), not down.
     void updateCachedAttributeValuesIfNeeded() const;