Pass FecControllerOverride to Vp8FrameBufferControllerFactory::Create

Previously, FecControllerOverride was passed to
Vp8FrameBufferController::SetFecControllerOverride. Passing to
the factory is a more elegant way, since it's only used when
the controller is constructed.

TBR=kwiberg@webrtc.org

Bug: webrtc:10769
Change-Id: Iae599889e7ca9003e3200c2911239cbb763ee65a
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/144380
Reviewed-by: Erik Språng <sprang@webrtc.org>
Commit-Queue: Elad Alon <eladalon@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#28443}
diff --git a/api/BUILD.gn b/api/BUILD.gn
index 77246bc..2ca55c7 100644
--- a/api/BUILD.gn
+++ b/api/BUILD.gn
@@ -649,6 +649,17 @@
     ]
   }
 
+  rtc_source_set("mock_fec_controller_override") {
+    testonly = true
+    sources = [
+      "test/mock_fec_controller_override.h",
+    ]
+    deps = [
+      ":fec_controller_api",
+      "../test:test_support",
+    ]
+  }
+
   rtc_source_set("mock_frame_encryptor") {
     testonly = true
     sources = [