[PresentationAPI] Implementing start/joinSession from WebPresentationClient to PresentationService.

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("//third_party/mojo/src/mojo/public/tools/bindings/mojom.gni")
 
 if (is_chromeos && current_cpu != "arm") {
@@ skipping 451 matching lines @@
     cflags = [ "/bigobj" ]
   }
 }
 
 mojom("mojo_bindings") {
   sources = [
     "application_setup.mojom",
     "geolocation_service.mojom",
     "permission_service.mojom",
     "presentation/presentation_service.mojom",
+    "presentation/presentation_session.mojom",
     "render_frame_setup.mojom",
   ]
 
   deps = [
     "//content/public/common:mojo_bindings",
     "//third_party/mojo/src/mojo/public/interfaces/application:application",
   ]
 }