Change other usages of .size() to .empty() when applicable.

chrome/test/url_fetch_test/url_fetch_test.cc

 // Copyright (c) 2011 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.
 
 #include "base/command_line.h"
 #include "base/file_path.h"
 #include "base/file_util.h"
 #include "base/path_service.h"
 #include "base/string_number_conversions.h"
 #include "base/string_util.h"
@@ skipping 159 matching lines @@
           cookie_value.length() > 0 ? cookie_value.c_str() : NULL,
           jsvar.length() > 0 ? jsvar.c_str() : NULL,
           js_expr,
           js_frame_xpath,
           js_timeout_ms,
           &result);
 
   // Write out the cookie if requested
   FilePath cookie_output_path =
       cmd_line->GetSwitchValuePath("wait_cookie_output");
-  if (cookie_output_path.value().size() > 0) {
+  if (!cookie_output_path.value().empty()) {
     ASSERT_TRUE(WriteValueToFile(result.cookie_value, cookie_output_path));
   }
 
   // Write out the JS Variable if requested
   FilePath jsvar_output_path = cmd_line->GetSwitchValuePath("jsvar_output");
-  if (jsvar_output_path.value().size() > 0) {
+  if (!jsvar_output_path.value().empty()) {
     ASSERT_TRUE(WriteValueToFile(result.javascript_variable,
                                  jsvar_output_path));
   }
 }
 
 }  // namespace