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

content/browser/BUILD.gn

Index: content/browser/BUILD.gn
diff --git a/content/browser/BUILD.gn b/content/browser/BUILD.gn
index b02a346282cf8edec482f9482b15815279f3fd31..20954fa29d0ed31dc462086178902d243b7e45c5 100644
--- a/content/browser/BUILD.gn
+++ b/content/browser/BUILD.gn
@@ -11,6 +11,12 @@ 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.
@@ -1587,6 +1593,22 @@ source_set("browser") {
     ]
   }
 
+  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) {