Add an extensions keep-alive client.

extensions/renderer/resources/extensions_renderer_resources.grd

 <?xml version="1.0" encoding="UTF-8"?>
 <grit latest_public_release="0" current_release="1">
   <outputs>
     <output filename="grit/extensions_renderer_resources.h" type="rc_header">
       <emit emit_type='prepend'></emit>
     </output>
     <output filename="extensions_renderer_resources.pak" type="data_package" />
   </outputs>
   <release seq="1">
     <includes>
       <!-- Extension libraries. -->
       <include name="IDR_APP_VIEW_DENY_JS" file="guest_view/app_view_deny.js" type="BINDATA" />
       <include name="IDR_APP_VIEW_JS" file="guest_view/app_view.js" type="BINDATA" />
       <include name="IDR_ASYNC_WAITER_JS" file="async_waiter.js" type="BINDATA" />
       <include name="IDR_DATA_RECEIVER_JS" file="data_receiver.js" type="BINDATA" />
       <include name="IDR_DATA_SENDER_JS" file="data_sender.js" type="BINDATA" />
       <include name="IDR_DATA_STREAM_MOJOM_JS" file="${mojom_root}\device\serial\data_stream.mojom.js" use_base_dir="false" type="BINDATA" />
       <include name="IDR_DATA_STREAM_SERIALIZATION_MOJOM_JS" file="${mojom_root}\device\serial\data_stream_serialization.mojom.js" use_base_dir="false" type="BINDATA" />
       <include name="IDR_ENTRY_ID_MANAGER" file="entry_id_manager.js" type="BINDATA" />
       <include name="IDR_EVENT_BINDINGS_JS" file="event.js" type="BINDATA" />
       <include name="IDR_IMAGE_UTIL_JS" file="image_util.js" type="BINDATA" />
       <include name="IDR_JSON_SCHEMA_JS" file="json_schema.js" type="BINDATA" />
+      <include name="IDR_KEEP_ALIVE_JS" file="keep_alive.js" type="BINDATA" />
+      <include name="IDR_KEEP_ALIVE_MOJOM_JS" file="${mojom_root}\extensions\common\mojo\keep_alive.mojom.js" use_base_dir="false" type="BINDATA" />
       <include name="IDR_LAST_ERROR_JS" file="last_error.js" type="BINDATA" />
       <include name="IDR_MESSAGING_JS" file="messaging.js" type="BINDATA" />
       <include name="IDR_MESSAGING_UTILS_JS" file="messaging_utils.js" type="BINDATA" />
       <include name="IDR_SCHEMA_UTILS_JS" file="schema_utils.js" type="BINDATA" />
       <include name="IDR_SEND_REQUEST_JS" file="send_request.js" type="BINDATA" />
       <include name="IDR_SERIAL_CUSTOM_BINDINGS_JS" file="serial_custom_bindings.js" type="BINDATA" />
       <include name="IDR_SERIAL_MOJOM_JS" file="${mojom_root}\device\serial\serial.mojom.js" use_base_dir="false" type="BINDATA" />
       <include name="IDR_SERIAL_SERIALIZATION_MOJOM_JS" file="${mojom_root}\device\serial\serial_serialization.mojom.js" use_base_dir="false" type="BINDATA" />
       <include name="IDR_SERIAL_SERVICE_JS" file="serial_service.js" type="BINDATA" />
       <include name="IDR_SET_ICON_JS" file="set_icon.js" type="BINDATA" />
@@ skipping 36 matching lines @@
 
       <!-- Extension styles. -->
       <include name="IDR_EXTENSION_FONTS_CSS" file="extension_fonts.css" type="BINDATA"/>
     </includes>
     <structures>
       <!-- Extension styles. -->
       <structure name="IDR_EXTENSION_CSS" file="extension.css" type="chrome_html" flattenhtml="true" />
     </structures>
   </release>
 </grit>