Convert MimeRegistry to use mojo.

third_party/WebKit/public/platform/mime_registry.mojom

Index: third_party/WebKit/public/platform/mime_registry.mojom
diff --git a/third_party/WebKit/public/platform/mime_registry.mojom b/third_party/WebKit/public/platform/mime_registry.mojom
new file mode 100644
index 0000000000000000000000000000000000000000..dbd258295723c3b23462f09c934c3cc35797aa58
--- /dev/null
+++ b/third_party/WebKit/public/platform/mime_registry.mojom
@@ -0,0 +1,10 @@
+// Copyright 2016 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.
+
+module blink.mojom;
+
+interface MimeRegistry {
+  [Sync]
+  GetMimeTypeFromExtension(string extension) => (string mime_type);
+};