Have a clearer error message for Android's GetMimeTypeFromExtension

net/android/network_library.cc

 // Copyright (c) 2012 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 "net/android/network_library.h"
 
 #include "base/android/jni_android.h"
 #include "base/android/jni_array.h"
 #include "base/android/jni_string.h"
 #include "base/android/scoped_java_ref.h"
@@ skipping 69 matching lines @@
                               std::string* result) {
   JNIEnv* env = AttachCurrentThread();
 
   ScopedJavaLocalRef<jstring> extension_string =
       ConvertUTF8ToJavaString(env, extension);
   ScopedJavaLocalRef<jstring> ret =
       Java_AndroidNetworkLibrary_getMimeTypeFromExtension(
           env, extension_string.obj());
 
   if (!ret.obj()) {
-    LOG(WARNING) << "Call to getMimeTypeFromExtension failed";
+    LOG(WARNING) << "Call to getMimeTypeFromExtension failed for extension: "
+        << extension;
     return false;
   }
   *result = ConvertJavaStringToUTF8(ret);
   return true;
 }
 
 bool RegisterNetworkLibrary(JNIEnv* env) {
   return RegisterNativesImpl(env);
 }
 
 }  // namespace android
 }  // namespace net