Make various string_util functions take StringPieces instead of char[].

chrome/browser/autocomplete/builtin_provider.cc

Index: chrome/browser/autocomplete/builtin_provider.cc
diff --git a/chrome/browser/autocomplete/builtin_provider.cc b/chrome/browser/autocomplete/builtin_provider.cc
index 5b35c75fa0317aa646997e622f0d0e11c2f752a2..df0fc434d451ec6c92644baaae757a76775e4c48 100644
--- a/chrome/browser/autocomplete/builtin_provider.cc
+++ b/chrome/browser/autocomplete/builtin_provider.cc
@@ -107,8 +107,7 @@ void BuiltinProvider::Start(const AutocompleteInput& input,
         !url.has_query() && !url.has_ref()) {
       // Include the path for sub-pages (e.g. "chrome://settings/browser").
       base::string16 host_and_path = base::UTF8ToUTF16(url.host() + url.path());
-      base::TrimString(host_and_path, base::ASCIIToUTF16("/").c_str(),
-                       &host_and_path);
+      base::TrimString(host_and_path, base::ASCIIToUTF16("/"), &host_and_path);
       size_t match_length = kChrome.length() + host_and_path.length();
       for (Builtins::const_iterator i(builtins_.begin());
           (i != builtins_.end()) && (matches_.size() < kMaxMatches); ++i) {