clang/win: Let some chromium_code targets build with -Wextra.

base/file_version_info_unittest.cc

Index: base/file_version_info_unittest.cc
diff --git a/base/file_version_info_unittest.cc b/base/file_version_info_unittest.cc
index c5e9859400316a31c651850c3defccc5c656f254..d4ab95416e199ae3f042f1d0f99eff45c3c411bf 100644
--- a/base/file_version_info_unittest.cc
+++ b/base/file_version_info_unittest.cc
@@ -93,7 +93,7 @@ TEST(FileVersionInfoTest, IsOfficialBuild) {
   // Test consistency check.
   ASSERT_EQ(arraysize(kDLLNames), arraysize(kExpected));
 
-  for (int i = 0; i < arraysize(kDLLNames); ++i) {
+  for (size_t i = 0; i < arraysize(kDLLNames); ++i) {
     FilePath dll_path = GetTestDataPath();
     dll_path = dll_path.Append(kDLLNames[i]);