message: Add tests for H264 SVC support
  The tests require H264 to be enabled using the proprietary_codecs
  GN args.gn option.
  Cr-Commit-Position: refs/heads/main@{#38133}
diff: @@ -47,6 +47,7 @@ using ScreenShareConfig = ::webrtc::webrtc_pc_e2e::
  using VideoCodecConfig = ::webrtc::webrtc_pc_e2e::
  PeerConnectionE2EQualityTestFixture::VideoCodecConfig;
  using ::cricket::kAv1CodecName;
  +using ::cricket::kH264CodecName;
  using ::cricket::kVp8CodecName;
  using ::cricket::kVp9CodecName;
  using ::testing::Combine;
  @@ -310,7 +311,22 @@ INSTANTIATE_TEST_SUITE_P(
  Values(UseDependencyDescriptor::Disabled,
  UseDependencyDescriptor::Enabled)),
  SvcTestNameGenerator);
  -#if RTC_ENABLE_VP9
  +
  +#if defined(WEBRTC_USE_H264)
  +INSTANTIATE_TEST_SUITE_P(
  + SvcTestH264,
  + SvcTest,
  + Combine(ValuesIn({
  + SvcTestParameters{kH264CodecName, "L1T1", 1, 1},
  + // SvcTestParameters{kH264CodecName, "L1T2", 1, 2},
  + // SvcTestParameters{kH264CodecName, "L1T3", 1, 3},
  + }),
  + Values(UseDependencyDescriptor::Disabled,
  + UseDependencyDescriptor::Enabled)),
  + SvcTestNameGenerator);
  +#endif
  +
  +#if defined(RTC_ENABLE_VP9)
  INSTANTIATE_TEST_SUITE_P(
  SvcTestVP9,
  SvcTest,
  