Move ViewHostMsg_GenerateRoutingID to mojom

BUG=612500
[email protected], [email protected]

Review-Url: https://codereview.chromium.org/2351333002
Cr-Commit-Position: refs/heads/master@{#420180}
diff --git a/content/common/BUILD.gn b/content/common/BUILD.gn
index 513213b..5591368 100644
--- a/content/common/BUILD.gn
+++ b/content/common/BUILD.gn
@@ -562,6 +562,7 @@
     "leveldb_wrapper.mojom",
     "memory_coordinator.mojom",
     "render_frame_message_filter.mojom",
+    "render_message_filter.mojom",
     "render_widget_window_tree_client_factory.mojom",
     "service_worker/embedded_worker_setup.mojom",
     "storage_partition_service.mojom",