[Video Capture Service] Change child flag for Video Capture Service on MacOS.

As suggested in http://crbug.com/990381, it should be beneficial to
change the child process flag for the video capture service on MacOS.
This is due to issues with entitlements.

This CL changes the flag of the utility process to CHILD_PLUGIN.

Bug: 990381
Change-Id: I31583c2860678d0fadee00f37cb1cfd089ce53a3
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1905848Reviewed-by: Bo <boliu@chromium.org>
Reviewed-by: Robert Sesek <rsesek@chromium.org>
Commit-Queue: Armando Miraglia <armax@chromium.org>
Cr-Commit-Position: refs/heads/master@{#715283}

content/browser/video_capture_service.cc

@@ -12,6 +12,7 @@
 #include "content/public/browser/browser_task_traits.h"
 #include "content/public/browser/browser_thread.h"
 #include "content/public/browser/service_process_host.h"
+#include "content/public/common/child_process_host.h"
 #include "content/public/common/content_features.h"
 #include "content/public/common/content_switches.h"
 #include "mojo/public/cpp/bindings/receiver_set.h"
@@ -112,6 +113,12 @@ video_capture::mojom::VideoCaptureService& GetVideoCaptureService() {
               // On Mac, the service requires a CFRunLoop which is provided by a
               // UI message loop. See https://crbug.com/834581.
               .WithExtraCommandLineSwitches({switches::kMessageLoopTypeUi})
+              // On Mac, the service also needs to have a different set of
+              // entitlements, the reason being that some virtual cameras
+              // are not signed or are signed by a different Team ID. Hence,
+              // library validation has to be disabled (see
+              // http://crbug.com/990381#c21).
+              .WithChildFlags(ChildProcessHost::CHILD_PLUGIN)
 #endif
               .Pass());