Remove unused blink::WebStorageArea::memoryBytesUsedByCache().

third_party/WebKit/public/platform/WebStorageArea.h

Index: third_party/WebKit/public/platform/WebStorageArea.h
diff --git a/third_party/WebKit/public/platform/WebStorageArea.h b/third_party/WebKit/public/platform/WebStorageArea.h
index 486909e5a499e72f3174b78c723220aa0149fb3b..432782943936f32604a4a3c688db4781cc402820 100644
--- a/third_party/WebKit/public/platform/WebStorageArea.h
+++ b/third_party/WebKit/public/platform/WebStorageArea.h
@@ -85,9 +85,6 @@ public:
         clear(pageUrl, unused);
     }
 
-    // Returns amount of bytes occupied by the storage cache in physical memory.
-    virtual size_t memoryBytesUsedByCache() const { return 0; }
-
     // DEPRECATED - being replaced by the async variants above which do not return oldValues or block until completion.
     virtual void setItem(const WebString& key, const WebString& newValue, const WebURL&, Result&, WebString& oldValue) { }
     virtual void removeItem(const WebString& key, const WebURL& pageUrl, WebString& oldValue)  { }