mojo: Make EqualsTraits<> part of public C++ API

mojo/public/cpp/bindings/BUILD.gn

 # Copyright 2014 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.
 
 interfaces_bindings_gen_dir = "$root_gen_dir/mojo/public/interfaces/bindings"
 
 component("bindings") {
   sources = [
     # Normally, targets should depend on the source_sets generated by mojom
     # targets. However, the generated source_sets use portions of the bindings
@@ skipping 21 matching lines @@
     "associated_interface_ptr.h",
     "associated_interface_ptr_info.h",
     "associated_interface_request.h",
     "binding.h",
     "binding_set.h",
     "bindings_export.h",
     "clone_traits.h",
     "connection_error_callback.h",
     "connector.h",
     "disconnect_reason.h",
+    "equals_traits.h",
     "filter_chain.h",
     "interface_data_view.h",
     "interface_endpoint_client.h",
     "interface_endpoint_controller.h",
     "interface_id.h",
     "interface_ptr.h",
     "interface_ptr_info.h",
     "interface_ptr_set.h",
     "interface_request.h",
     "lib/array_internal.cc",
     "lib/array_internal.h",
     "lib/array_serialization.h",
     "lib/associated_binding.cc",
     "lib/associated_group.cc",
     "lib/associated_group_controller.cc",
     "lib/associated_interface_ptr.cc",
     "lib/associated_interface_ptr_state.h",
     "lib/binding_state.cc",
     "lib/binding_state.h",
     "lib/bindings_internal.h",
     "lib/buffer.h",
     "lib/connector.cc",
     "lib/control_message_handler.cc",
     "lib/control_message_handler.h",
     "lib/control_message_proxy.cc",
     "lib/control_message_proxy.h",
-    "lib/equals_traits.h",
     "lib/filter_chain.cc",
     "lib/fixed_buffer.cc",
     "lib/fixed_buffer.h",
     "lib/handle_interface_serialization.h",
     "lib/hash_util.h",
     "lib/interface_endpoint_client.cc",
     "lib/interface_ptr_state.h",
     "lib/map_data_internal.h",
     "lib/map_serialization.h",
     "lib/may_auto_lock.h",
@@ skipping 105 matching lines @@
     ]
 
     public_deps = [
       ":bindings",
       "//third_party/WebKit/Source/platform/wtf",
     ]
 
     public_configs = [ "//third_party/WebKit/Source:config" ]
   }
 }