Have a clearer error message for Android's GetMimeTypeFromExtension

net/android/network_library.cc

Index: net/android/network_library.cc
diff --git a/net/android/network_library.cc b/net/android/network_library.cc
index 64f11aa5349402745f29711e75b2cbdee1bf2aa0..ce5567928b4b4a8110ecc643f4b9e14e9d5cf67f 100644
--- a/net/android/network_library.cc
+++ b/net/android/network_library.cc
@@ -87,7 +87,8 @@ bool GetMimeTypeFromExtension(const std::string& extension,
           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);