message: Fix dependency templates for VP8 3 temporal layers
  Cr-Commit-Position: refs/heads/master@{#30692}
diff: @@ -164,6 +164,12 @@ DefaultTemporalLayers::GetDependencyInfo(size_t num_layers) {
  // TL1 references 'last' and references and updates 'golden'.
  // TL2 references both 'last' & 'golden' and references and updates
  // 'arf'.
  + // 2-------2 2-------2 2
  + // / __/ / __/ /
  + // / __1 / __1 /
  + // /___/ /___/ /
  + // 0---------------0---------------0-----
  + // 0 1 2 3 4 5 6 7 8 9 ...
  return {{"SSS", {kReferenceAndUpdate, kNone, kNone}},
  {"--S", {kReference, kNone, kUpdate}},
  {"-DR", {kReference, kUpdate, kNone}},
  @@ -174,6 +180,12 @@ DefaultTemporalLayers::GetDependencyInfo(size_t num_layers) {
  // TL0 also references and updates the 'last' buffer.
  // TL1 also references 'last' and references and updates 'golden'.
  // TL2 references both 'last' and 'golden' but updates no buffer.
  + // 2 __2 _____2 __2 2
  + // / /____/ / / /
  + // / 1---------/-----1 /
  + // /_____/ /_____/ /
  + // 0---------------0---------------0-----
  + // 0 1 2 3 4 5 6 7 8 9 ...
  return {{"SSS", {kReferenceAndUpdate, kNone, kNone}},
  {"--D", {kReference, kNone, kNone, kFreezeEntropy}},
  {"-SS", {kReference, kUpdate, kNone}},
  @@ -616,15 +628,25 @@ FrameDependencyStructure DefaultTemporalLayers::GetTemplateStructure(
  return template_structure;
  }
  case 3: {
  + if (field_trial::IsEnabled("WebRTC-UseShortVP8TL3Pattern")) {
  + template_structure.templates = {
  + Builder().T(0).Dtis("SSS").Build(),
  + Builder().T(0).Dtis("SSS").Fdiffs({4}).Build(),
  + Builder().T(1).Dtis("-DR").Fdiffs({2}).Build(),
  + Builder().T(2).Dtis("--S").Fdiffs({1}).Build(),
  + Builder().T(2).Dtis("--D").Fdiffs({1, 2}).Build(),
  + };
  + } else {
  template_structure.templates = {
  Builder().T(0).Dtis("SSS").Build(),
  Builder().T(0).Dtis("SSS").Fdiffs({4}).Build(),
  Builder().T(0).Dtis("SRR").Fdiffs({4}).Build(),
  - Builder().T(1).Dtis("-SR").Fdiffs({2}).Build(),
  - Builder().T(1).Dtis("-DR").Fdiffs({2, 4}).Build(),
  + Builder().T(1).Dtis("-SS").Fdiffs({2}).Build(),
  + Builder().T(1).Dtis("-DS").Fdiffs({2, 4}).Build(),
  Builder().T(2).Dtis("--D").Fdiffs({1}).Build(),
  Builder().T(2).Dtis("--D").Fdiffs({1, 3}).Build(),
  };
  + }
  return template_structure;
  }
  case 4: {
  