Remove undefined method AXObjectCache::focusedObject.

Also remove unused forward declaration of AXObject.

Review-Url: https://codereview.chromium.org/2589263002
Cr-Commit-Position: refs/heads/master@{#439858}

third_party/WebKit/Source/core/dom/AXObjectCache.h

@@ -36,7 +36,6 @@ typedef unsigned AXID;
 namespace blink {
 
 class AbstractInlineTextBox;
-class AXObject;
 class FrameView;
 class HTMLCanvasElement;
 class HTMLOptionElement;
@@ -51,8 +50,6 @@ class CORE_EXPORT AXObjectCache
  public:
   static AXObjectCache* create(Document&);
 
-  static AXObject* focusedObject();
-
   virtual ~AXObjectCache();
   DEFINE_INLINE_VIRTUAL_TRACE() {}