Add timing info to all encoded frames.

Even if we're not going to transmit any timing info over the wire.

Bug: webrtc:8504
Change-Id: Id54192a10e6b2a6a2cb57a2ff6b28fc0d16e471d
Reviewed-on: https://webrtc-review.googlesource.com/21160
Reviewed-by: Per Kjellander <perkj@webrtc.org>
Reviewed-by: Ilya Nikolaevskiy <ilnik@webrtc.org>
Reviewed-by: Erik Språng <sprang@webrtc.org>
Commit-Queue: Niels Moller <nisse@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#20628}

modules/video_coding/generic_encoder_unittest.cc

@@ -33,7 +33,8 @@ class FakeEncodedImageCallback : public EncodedImageCallback {
                         const CodecSpecificInfo* codec_specific_info,
                         const RTPFragmentationHeader* fragmentation) override {
     last_frame_was_timing_ =
-        encoded_image.timing_.flags != TimingFrameFlags::kInvalid;
+        encoded_image.timing_.flags != TimingFrameFlags::kInvalid &&
+        encoded_image.timing_.flags != TimingFrameFlags::kNotTriggered;
     return Result(Result::OK);
   };