Public Sessions - prompt the user for tabCapture requests

In Public Sessions, extensions (and apps) are force-installed by admin policy so the user does not get a chance to review the permissions for these extensions. This is not acceptable from a security/privacy standpoint, so when an extension uses the TabCapture API for the first time, we show the user a dialog where they can choose whether to allow the extension access to the API.

This CL will also whitelist desktopCapture manifest permission feature as it's already safe in its current form (user is prompted) together with tabCapture.

BUG=672093

Review-Url: https://codereview.chromium.org/2558843002
Cr-Commit-Position: refs/heads/master@{#438594}
diff --git a/chrome/browser/BUILD.gn b/chrome/browser/BUILD.gn
index 4ff6479ef..8816e0e8 100644
--- a/chrome/browser/BUILD.gn
+++ b/chrome/browser/BUILD.gn
@@ -2159,6 +2159,8 @@
       "download/notification/download_notification_manager.h",
       "media/public_session_media_access_handler.cc",
       "media/public_session_media_access_handler.h",
+      "media/webrtc/public_session_tab_capture_access_handler.cc",
+      "media/webrtc/public_session_tab_capture_access_handler.h",
       "memory/memory_kills_histogram.h",
       "memory/memory_kills_monitor.cc",
       "memory/memory_kills_monitor.h",