Remove deprecated updateBackingStoreAndCheckValidity from WebAXObject

public/web/WebAXObject.h

Index: public/web/WebAXObject.h
diff --git a/public/web/WebAXObject.h b/public/web/WebAXObject.h
index 8cd0788f4a73454523988b089432a4c887da8d32..7e19f10443ffd9e74627828f2e0efee2fd36d9f1 100644
--- a/public/web/WebAXObject.h
+++ b/public/web/WebAXObject.h
@@ -76,13 +76,9 @@ public:
     // Update layout on the underlying tree, and return true if this object is
     // still valid (not detached). Note that calling this method
     // can cause other WebAXObjects to become invalid, too,
-    // so always call isDetached if updateBackingStoreAndCheckValidity
-    // has been called on any object, or if any other WebCore code has run.
+    // so always call isDetached if any other WebCore code has run.
     BLINK_EXPORT bool updateLayoutAndCheckValidity();
 
-    // FIXME: Deprecated - remove once callers use updateLayoutAndCheckValidity, instead.
-    BLINK_EXPORT bool updateBackingStoreAndCheckValidity();
-
     BLINK_EXPORT WebString accessibilityDescription() const;
     BLINK_EXPORT unsigned childCount() const;