Provide a std::vector compliant empty() method for WebVector.

third_party/WebKit/Source/web/WebDocument.cpp

 /*
  * Copyright (C) 2009 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 176 matching lines @@
   DCHECK(document);
   StyleSheetContents* parsedSheet =
       StyleSheetContents::create(CSSParserContext::create(*document));
   parsedSheet->parseString(sourceCode);
   document->styleEngine().injectAuthorSheet(parsedSheet);
 }
 
 void WebDocument::watchCSSSelectors(const WebVector<WebString>& webSelectors) {
   Document* document = unwrap<Document>();
   CSSSelectorWatch* watch = CSSSelectorWatch::fromIfExists(*document);
-  if (!watch && webSelectors.isEmpty())
+  if (!watch && webSelectors.empty())
     return;
   Vector<String> selectors;
   selectors.append(webSelectors.data(), webSelectors.size());
   CSSSelectorWatch::from(*document).watchCSSSelectors(selectors);
 }
 
 WebReferrerPolicy WebDocument::getReferrerPolicy() const {
   return static_cast<WebReferrerPolicy>(
       constUnwrap<Document>()->getReferrerPolicy());
 }
@@ skipping 88 matching lines @@
 WebDocument& WebDocument::operator=(Document* elem) {
   m_private = elem;
   return *this;
 }
 
 WebDocument::operator Document*() const {
   return toDocument(m_private.get());
 }
 
 }  // namespace blink