Replace base::str[n]casecmp with helper functions.

components/mime_util/mime_util.cc

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "components/mime_util/mime_util.h"
 
 #include "base/containers/hash_tables.h"
 #include "base/lazy_instance.h"
 #include "base/strings/string_util.h"
 #include "build/build_config.h"
@@ skipping 203 matching lines @@
 
 bool IsSupportedMimeType(const std::string& mime_type) {
   return g_mime_util.Get().IsSupportedMimeType(mime_type);
 }
 
 net::CertificateMimeType GetCertificateMimeTypeForMimeType(
     const std::string& mime_type) {
   // Don't create a map, there is only one entry in the table,
   // except on Android.
   for (size_t i = 0; i < arraysize(kSupportedCertificateTypes); ++i) {
-    if (base::strcasecmp(mime_type.c_str(),
-                         kSupportedCertificateTypes[i].mime_type) == 0) {
+    if (base::EqualsCaseInsensitiveASCII(
+            mime_type, kSupportedCertificateTypes[i].mime_type)) {
       return kSupportedCertificateTypes[i].cert_type;
     }
   }
 
   return net::CERTIFICATE_MIME_TYPE_UNKNOWN;
 }
 
 }  // namespace mime_util