libchrome: Several upstreamable fixes from libchrome

base/files/file_path.cc

Index: base/files/file_path.cc
diff --git a/base/files/file_path.cc b/base/files/file_path.cc
index 2c199e131a56ee1976dded1dd25af158ac1c6252..8180f570f8cb7f7496b36c680be0ceaea6afb859 100644
--- a/base/files/file_path.cc
+++ b/base/files/file_path.cc
@@ -53,6 +53,9 @@ StringPieceType::size_type FindDriveLetter(StringPieceType path) {
        (path[0] >= L'a' && path[0] <= L'z'))) {
     return 1;
   }
+#else
+  // Avoid an unused warning.
+  (void)path;
 #endif  // FILE_PATH_USES_DRIVE_LETTERS
   return StringType::npos;
 }
@@ -1319,6 +1322,8 @@ FilePath FilePath::NormalizePathSeparatorsTo(CharType separator) const {
   }
   return FilePath(copy);
 #else
+  // Avoid an unused warning.
+  (void)separator;
   return *this;
 #endif
 }