Tightening visibility and removing a public_dep.

This CL aligns the visibility and the dependency between the _objc
and the _generic targets to the standard decided in:
https://codereview.webrtc.org/3001623003.

BUG=webrtc:7743

Review-Url: https://codereview.webrtc.org/3010133002
Cr-Commit-Position: refs/heads/master@{#19687}

webrtc/video/BUILD.gn

diff --git a/webrtc/video/BUILD.gn b/webrtc/video/BUILD.gn
index f3bba0e..c93ef8c 100644
--- a/webrtc/video/BUILD.gn
+++ b/webrtc/video/BUILD.gn
@@ -165,6 +165,7 @@
       "../system_wrappers:metrics_default",
       "../test:field_trial",
       "../test:run_test",
+      "../test:run_test_interface",
       "../test:test_common",
       "../test:test_renderer",
       "../test:test_support",
@@ -189,6 +190,7 @@
       "../system_wrappers:metrics_default",
       "../test:field_trial",
       "../test:run_test",
+      "../test:run_test_interface",
       "../test:test_common",
       "../test:test_renderer",
       "../test:test_support",
@@ -218,6 +220,7 @@
       "../test:field_trial",
       "../test:rtp_test_utils",
       "../test:run_test",
+      "../test:run_test_interface",
       "../test:test_common",
       "../test:test_renderer",
       "../test:test_support",