[Mojo Video Capture] Implement a VideoCaptureProvider using the Mojo service (part 1)

content/browser/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("//gpu/vulkan/features.gni")
 import("//media/media_options.gni")
 import("//ppapi/features/features.gni")
 import("//printing/features/features.gni")
 import("//third_party/WebKit/public/public_features.gni")
 import("//tools/ipc_fuzzer/ipc_fuzzer.gni")
 
+declare_args() {
+  # Include code in the build that is only needed when using the video
+  # capture Mojo service, which is currently experimental.
+  enable_mojo_video_capture = false
+}
+
 source_set("browser") {
   # Only the public target should depend on this. All other targets (even
   # internal content ones) should depend on the public one.
   visibility = [
     ":for_content_tests",  # See top of //content/BUILD.gn for why.
     "//content/app:*",
     "//content/public/browser:browser_sources",
   ]
 
   configs += [
@@ skipping 1556 matching lines @@
 
     deps += [
       "//jingle:jingle_glue",
       "//third_party/webrtc/base:rtc_base",
       "//third_party/webrtc/media:rtc_media_base",
       "//third_party/webrtc/modules/desktop_capture:primitives",
       "//third_party/webrtc_overrides:init_webrtc",
     ]
   }
 
+  if (enable_mojo_video_capture) {
+    sources += [
+      "renderer_host/media/service_launched_video_capture_device.cc",
+      "renderer_host/media/service_launched_video_capture_device.h",
+      "renderer_host/media/service_video_capture_device_launcher.cc",
+      "renderer_host/media/service_video_capture_device_launcher.h",
+      "renderer_host/media/service_video_capture_provider.cc",
+      "renderer_host/media/service_video_capture_provider.h",
+    ]
+
+    deps += [
+      "//services/video_capture/public/cpp",
+      "//services/video_capture/public/interfaces:constants",
+    ]
+  }
+
   # Desktop screen capture implementations, conditionally built depending on
   # the available implementations for each platform.
   if (is_linux || is_mac || is_win) {
     defines += [ "ENABLE_SCREEN_CAPTURE=1" ]
     sources += [
       "media/capture/cursor_renderer.cc",
       "media/capture/cursor_renderer.h",
       "media/capture/web_contents_video_capture_device.cc",
       "media/capture/web_contents_video_capture_device.h",
       "media/capture/window_activity_tracker.cc",
@@ skipping 493 matching lines @@
   if (!is_component_build) {
     public_deps = [
       ":browser",
     ]
   } else {
     public_deps = [
       "//third_party/leveldatabase",
     ]
   }
 }