Support exporting Mojo bindings for the component build.

content/common/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("//build/config/features.gni")
 import("//build/config/ui.gni")
 import("//content/common/common.gni")
 import("//media/media_options.gni")
 import("//mojo/public/tools/bindings/mojom.gni")
 import("//tools/ipc_fuzzer/ipc_fuzzer.gni")
@@ skipping 216 matching lines @@
 group("for_content_tests") {
   visibility = [ "//content/test/*" ]
   if (!is_component_build) {
     public_deps = [
       ":common",
     ]
   }
 }
 
 mojom("mojo_bindings") {
-  # This interface is internal to content. However, this is not exported from
-  # the content component shared library. Code in content but outside of the
-  # content component (content/test or content/shell) should link to this
-  # directly.
+  # This interface is internal to content.
   visibility = [ "//content/*" ]
 
   sources = [
     "frame.mojom",
     "image_downloader/image_downloader.mojom",
     "leveldb_wrapper.mojom",
     "process_control.mojom",
     "render_frame_message_filter.mojom",
     "render_widget_window_tree_client_factory.mojom",
     "service_worker/embedded_worker_setup.mojom",
     "storage_partition_service.mojom",
     "websocket.mojom",
   ]
 
   import_dirs = [ "//mojo/services" ]
 
   public_deps = [
     "//components/leveldb/public/interfaces",
     "//device/sensors/public/interfaces",
     "//services/shell/public/interfaces",
     "//services/ui/public/interfaces",
     "//skia/public/interfaces",
     "//third_party/WebKit/public:mojo_bindings",
     "//ui/gfx/geometry/mojo",
     "//url/mojo:url_mojom_gurl",
     "//url/mojo:url_mojom_origin",
   ]
 
   use_new_wrapper_types = false
+
+  export_class_attribute = "CONTENT_EXPORT"
+  export_define = "CONTENT_IMPLEMENTATION=1"
+  export_header = "content/common/content_export.h"
 }