Use copy-swap idiom for GURL::operator=

url/gurl.h

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef URL_GURL_H_
 #define URL_GURL_H_
 
 #include <iosfwd>
 #include <string>
 
@@ skipping 35 matching lines @@
   // from WebURL without copying the string. When we call this constructor
   // we pass in a temporary std::string, which lets the compiler skip the
   // copy and just move the std::string into the function argument. In the
   // implementation, we use swap to move the data into the GURL itself,
   // which means we end up with zero copies.
   GURL(std::string canonical_spec,
        const url_parse::Parsed& parsed, bool is_valid);
 
   ~GURL();
 
-  GURL& operator=(const GURL& other);
+  GURL& operator=(GURL other);
 
   // Returns true when this object represents a valid parsed URL. When not
   // valid, other functions will still succeed, but you will not get canonical
   // data out in the format you may be expecting. Instead, we keep something
   // "reasonable looking" so that the user can see how it's busted if
   // displayed to them.
   bool is_valid() const {
     return is_valid_;
   }
 
@@ skipping 306 matching lines @@
   // Used for nested schemes [currently only filesystem:].
   scoped_ptr<GURL> inner_url_;
 
   // TODO bug 684583: Add encoding for query params.
 };
 
 // Stream operator so GURL can be used in assertion statements.
 URL_EXPORT std::ostream& operator<<(std::ostream& out, const GURL& url);
 
 #endif  // URL_GURL_H_