Remove unused code from WebMimeRegistry.

content/child/simple_webmimeregistry_impl.cc

Index: content/child/simple_webmimeregistry_impl.cc
diff --git a/content/child/simple_webmimeregistry_impl.cc b/content/child/simple_webmimeregistry_impl.cc
index 98936816a9c2143fbd1b720fb4f3ae22fbf3c6e8..d65a0ccfe4ecee3c0d60a32c422e80ceec49df9d 100644
--- a/content/child/simple_webmimeregistry_impl.cc
+++ b/content/child/simple_webmimeregistry_impl.cc
@@ -99,12 +99,4 @@ WebString SimpleWebMimeRegistryImpl::wellKnownMimeTypeForExtension(
   return WebString::fromUTF8(mime_type);
 }
 
-WebString SimpleWebMimeRegistryImpl::mimeTypeFromFile(
-    const WebString& file_path) {
-  std::string mime_type;
-  net::GetMimeTypeFromFile(base::FilePath::FromUTF16Unsafe(file_path),
-                           &mime_type);
-  return WebString::fromUTF8(mime_type);
-}
-
 }  // namespace content