Add VideoProcessor tests verifying that H.264 keyframes contain SPS/PPS/IDR.

This CL adds an EncodedFrameChecker interface which can be used by users
of the VideoProcessor to inject customized per-frame checks to the
encoding/decoding pipeline. This currently has two uses:
- Verifying that the QP parser works correctly for VP8 and VP9, by comparing the
  parsed QP to that produced by libvpx.
- Verifying that our H.264 encoders always produce SPS/PPS/IDR in tandem.

TESTED=Galaxy S8, Pixel 2 XL, iPhone 7.
BUG=webrtc:8423

Change-Id: Ic3e401546e239a9ffaf2ed2907689cebb1127805
Reviewed-on: https://webrtc-review.googlesource.com/14559
Reviewed-by: Åsa Persson <asapersson@webrtc.org>
Reviewed-by: Sergey Silkin <ssilkin@webrtc.org>
Commit-Queue: Rasmus Brandt <brandtr@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#20409}

modules/video_coding/codecs/test/videoprocessor_integrationtest.h

@@ -16,6 +16,7 @@
 #include <vector>
 
 #include "common_types.h"  // NOLINT(build/include)
+#include "common_video/h264/h264_common.h"
 #include "media/engine/webrtcvideodecoderfactory.h"
 #include "media/engine/webrtcvideoencoderfactory.h"
 #include "modules/video_coding/codecs/test/packet_manipulator.h"
@@ -91,6 +92,13 @@ struct VisualizationParams {
 // or breakdown occurs.
 class VideoProcessorIntegrationTest : public testing::Test {
  protected:
+  // Verifies that all H.264 keyframes contain SPS/PPS/IDR NALUs.
+  class H264KeyframeChecker : public TestConfig::EncodedFrameChecker {
+   public:
+    void CheckEncodedFrame(webrtc::VideoCodecType codec,
+                           const EncodedImage& encoded_frame) const override;
+  };
+
   VideoProcessorIntegrationTest();
   ~VideoProcessorIntegrationTest() override;
 
@@ -104,6 +112,9 @@ class VideoProcessorIntegrationTest : public testing::Test {
   // Config.
   TestConfig config_;
 
+  // Can be used by all H.264 tests.
+  const H264KeyframeChecker h264_keyframe_checker_;
+
  private:
   class CpuProcessTime;
   static const int kMaxNumTemporalLayers = 3;