clang/win: Build chromium_code with -Wunused-function

win8/metro_driver/metro_driver.cc

Index: win8/metro_driver/metro_driver.cc
diff --git a/win8/metro_driver/metro_driver.cc b/win8/metro_driver/metro_driver.cc
index 4eedfdc0ae31d9a6b7f99f28601691debfdb85f8..650b23837612ff9539939730c9b113da5a24c525 100644
--- a/win8/metro_driver/metro_driver.cc
+++ b/win8/metro_driver/metro_driver.cc
@@ -18,6 +18,7 @@
 
 namespace {
 
+#if !defined(NDEBUG)
 LONG WINAPI ErrorReportingHandler(EXCEPTION_POINTERS* ex_info) {
   // See roerrorapi.h for a description of the
   // exception codes and parameters.
@@ -34,6 +35,7 @@ LONG WINAPI ErrorReportingHandler(EXCEPTION_POINTERS* ex_info) {
 
   return EXCEPTION_CONTINUE_SEARCH;
 }
+#endif
 
 void SetMetroReportingFlags() {
 #if !defined(NDEBUG)