NiceMock MockFecController in VideoStreamEncoderUnittests

The MockFecController is spitting out lots of warnings, as it is
being called when we don't care about it, in normal tests. Making
it a NiceMock allows it to receive calls without expectation and
not warn.

Bug: None
Change-Id: I1ea219c4665d86917718692dc013ae3ac47222ad
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/170600
Reviewed-by: Henrik Boström <hbos@webrtc.org>
Reviewed-by: Elad Alon <eladalon@webrtc.org>
Reviewed-by: Erik Språng <sprang@webrtc.org>
Commit-Queue: Evan Shrubsole <eshr@google.com>
Cr-Commit-Position: refs/heads/master@{#30820}
diff --git a/video/video_stream_encoder_unittest.cc b/video/video_stream_encoder_unittest.cc
index 9d6925e..934bf09 100644
--- a/video/video_stream_encoder_unittest.cc
+++ b/video/video_stream_encoder_unittest.cc
@@ -999,7 +999,7 @@
     bool expect_null_frame_ = false;
     EncodedImageCallback* encoded_image_callback_
         RTC_GUARDED_BY(local_crit_sect_) = nullptr;
-    MockFecControllerOverride fec_controller_override_;
+    NiceMock<MockFecControllerOverride> fec_controller_override_;
     int num_encoder_initializations_ RTC_GUARDED_BY(local_crit_sect_) = 0;
     std::vector<ResolutionBitrateLimits> resolution_bitrate_limits_
         RTC_GUARDED_BY(local_crit_sect_);