Add base:: to string16s in win8/.

win8/metro_driver/winrt_utils.h

Index: win8/metro_driver/winrt_utils.h
diff --git a/win8/metro_driver/winrt_utils.h b/win8/metro_driver/winrt_utils.h
index 3016c852e88a3b54a98852de1177868c6b63f149..e3a777f9bc9cc3a2ff9a95e029c5a150c7bf8045 100644
--- a/win8/metro_driver/winrt_utils.h
+++ b/win8/metro_driver/winrt_utils.h
@@ -14,9 +14,9 @@
 
 void CheckHR(HRESULT hr, const char* str = nullptr);
 
-HSTRING MakeHString(const string16& str);
+HSTRING MakeHString(const base::string16& str);
 
-string16 MakeStdWString(HSTRING hstring);
+base::string16 MakeStdWString(HSTRING hstring);
 
 namespace winrt_utils {
 
@@ -53,7 +53,7 @@ HRESULT CompareProperties(
 // shortcut's command line. This is intended for scenarios where those shortcut
 // parameters are ordinarily ignored (i.e. metro apps on win8). Returns an
 // empty string on failure.
-string16 ReadArgumentsFromPinnedTaskbarShortcut();
+base::string16 ReadArgumentsFromPinnedTaskbarShortcut();
 
 }  // namespace winrt_utils