Rewrite std::string("") to std::string(), Linux edition.

chrome/common/extensions/extension_unittest.cc

Index: chrome/common/extensions/extension_unittest.cc
diff --git a/chrome/common/extensions/extension_unittest.cc b/chrome/common/extensions/extension_unittest.cc
index 6a3c80d2ec02db4ad06f9e22212e1928dd7d0a09..edf24c45e222f73bc2747ff427b4b625fa3c7b54 100644
--- a/chrome/common/extensions/extension_unittest.cc
+++ b/chrome/common/extensions/extension_unittest.cc
@@ -233,16 +233,22 @@ TEST_F(ExtensionTest, MimeTypeSniffing) {
   ASSERT_TRUE(file_util::ReadFileToString(path, &data));
 
   std::string result;
-  EXPECT_TRUE(net::SniffMimeType(data.c_str(), data.size(),
-              GURL("http://www.example.com/foo.crx"), "", &result));
+  EXPECT_TRUE(net::SniffMimeType(data.c_str(),
+                                 data.size(),
+                                 GURL("http://www.example.com/foo.crx"),
+                                 std::string(),
+                                 &result));
   EXPECT_EQ(std::string(Extension::kMimeType), result);
 
   data.clear();
   result.clear();
   path = path.DirName().AppendASCII("bad_magic.crx");
   ASSERT_TRUE(file_util::ReadFileToString(path, &data));
-  EXPECT_TRUE(net::SniffMimeType(data.c_str(), data.size(),
-              GURL("http://www.example.com/foo.crx"), "", &result));
+  EXPECT_TRUE(net::SniffMimeType(data.c_str(),
+                                 data.size(),
+                                 GURL("http://www.example.com/foo.crx"),
+                                 std::string(),
+                                 &result));
   EXPECT_EQ("application/octet-stream", result);
 }