Link blink mojom bindings into platform target

content/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.
 
 import("//tools/grit/grit_rule.gni")
 import("//build/config/nacl/config.gni")
 
 # Applied by targets internal to content.
 config("content_implementation") {
   defines = [ "CONTENT_IMPLEMENTATION" ]
@@ skipping 111 matching lines @@
     "//content/public/app:renderer_manifest",
     "//content/public/app:utility_manifest",
     "//services/catalog:manifest",
   ]
 }
 
 # This target exists to "hold" the content_export header so we can do proper
 # inclusion testing of it.
 source_set("export") {
   # Must only be used inside of content.
-  visibility = [ "//content/*" ]
+  visibility = [
+    "//content/*",
+    # Because of typemap.
+    "//third_party/WebKit/Source/platform:mojo_bindings_cpp_sources",
+  ]
   sources = [
     "common/content_export.h",
   ]
 }
 
 # In the GYP build, this file is listed in several targets. In GN just have
 # those targets depend on this one. This can be depended on for any
 # platform for simplicity, and is a no-op on non-Windows.
 source_set("sandbox_helper_win") {
   if (is_win) {
     sources = [
       "app/sandbox_helper_win.cc",
       "public/app/sandbox_helper_win.h",
     ]
 
     deps = [
       "//sandbox",
     ]
   }
 }