Put iOS H264 High profile under a field trial

H264 High profile is causing problems for some downstream apps. Therefore,
put it behind a field trial instead.

BUG=webrtc:6337

Review-Url: https://codereview.webrtc.org/2580963004
Cr-Commit-Position: refs/heads/master@{#15663}
diff --git a/webrtc/sdk/objc/Framework/Classes/RTCFieldTrials.mm b/webrtc/sdk/objc/Framework/Classes/RTCFieldTrials.mm
index 224f7fd..89cf3c8 100644
--- a/webrtc/sdk/objc/Framework/Classes/RTCFieldTrials.mm
+++ b/webrtc/sdk/objc/Framework/Classes/RTCFieldTrials.mm
@@ -20,6 +20,7 @@
 NSString * const kRTCFieldTrialFlexFec03Key = @"WebRTC-FlexFEC-03";
 NSString * const kRTCFieldTrialImprovedBitrateEstimateKey = @"WebRTC-ImprovedBitrateEstimate";
 NSString * const kRTCFieldTrialTrendlineFilterKey = @"WebRTC-BweTrendlineFilter";
+NSString * const kRTCFieldTrialH264HighProfileKey = @"WebRTC-H264HighProfile";
 NSString * const kRTCFieldTrialEnabledValue = @"Enabled";
 
 static std::unique_ptr<char[]> gFieldTrialInitString;
diff --git a/webrtc/sdk/objc/Framework/Classes/videotoolboxvideocodecfactory.cc b/webrtc/sdk/objc/Framework/Classes/videotoolboxvideocodecfactory.cc
index b94194f..4027399 100644
--- a/webrtc/sdk/objc/Framework/Classes/videotoolboxvideocodecfactory.cc
+++ b/webrtc/sdk/objc/Framework/Classes/videotoolboxvideocodecfactory.cc
@@ -12,37 +12,23 @@
 #include "webrtc/base/logging.h"
 #include "webrtc/common_video/h264/profile_level_id.h"
 #include "webrtc/media/base/codec.h"
-#include "webrtc/sdk/objc/Framework/Classes/h264_video_toolbox_encoder.h"
 #include "webrtc/sdk/objc/Framework/Classes/h264_video_toolbox_decoder.h"
+#include "webrtc/sdk/objc/Framework/Classes/h264_video_toolbox_encoder.h"
+#include "webrtc/system_wrappers/include/field_trial.h"
 
 namespace webrtc {
 
+namespace {
+const char kHighProfileExperiment[] = "WebRTC-H264HighProfile";
+
+bool IsHighProfileEnabled() {
+  return field_trial::FindFullName(kHighProfileExperiment) == "Enabled";
+}
+}
+
 // VideoToolboxVideoEncoderFactory
 
 VideoToolboxVideoEncoderFactory::VideoToolboxVideoEncoderFactory() {
-  // TODO(magjed): Enumerate actual level instead of using hardcoded level 3.1.
-  // Level 3.1 is 1280x720@30fps which is enough for now.
-  const H264::Level level = H264::kLevel3_1;
-
-  cricket::VideoCodec constrained_high(cricket::kH264CodecName);
-  const H264::ProfileLevelId constrained_high_profile(
-      H264::kProfileConstrainedHigh, level);
-  constrained_high.SetParam(
-      cricket::kH264FmtpProfileLevelId,
-      *H264::ProfileLevelIdToString(constrained_high_profile));
-  constrained_high.SetParam(cricket::kH264FmtpLevelAsymmetryAllowed, "1");
-  constrained_high.SetParam(cricket::kH264FmtpPacketizationMode, "1");
-  supported_codecs_.push_back(constrained_high);
-
-  cricket::VideoCodec constrained_baseline(cricket::kH264CodecName);
-  const H264::ProfileLevelId constrained_baseline_profile(
-      H264::kProfileConstrainedBaseline, level);
-  constrained_baseline.SetParam(
-      cricket::kH264FmtpProfileLevelId,
-      *H264::ProfileLevelIdToString(constrained_baseline_profile));
-  constrained_baseline.SetParam(cricket::kH264FmtpLevelAsymmetryAllowed, "1");
-  constrained_baseline.SetParam(cricket::kH264FmtpPacketizationMode, "1");
-  supported_codecs_.push_back(constrained_baseline);
 }
 
 VideoToolboxVideoEncoderFactory::~VideoToolboxVideoEncoderFactory() {}
@@ -65,6 +51,34 @@
 
 const std::vector<cricket::VideoCodec>&
 VideoToolboxVideoEncoderFactory::supported_codecs() const {
+  supported_codecs_.clear();
+
+  // TODO(magjed): Enumerate actual level instead of using hardcoded level 3.1.
+  // Level 3.1 is 1280x720@30fps which is enough for now.
+  const H264::Level level = H264::kLevel3_1;
+
+  if (IsHighProfileEnabled()) {
+    cricket::VideoCodec constrained_high(cricket::kH264CodecName);
+    const H264::ProfileLevelId constrained_high_profile(
+        H264::kProfileConstrainedHigh, level);
+    constrained_high.SetParam(
+        cricket::kH264FmtpProfileLevelId,
+        *H264::ProfileLevelIdToString(constrained_high_profile));
+    constrained_high.SetParam(cricket::kH264FmtpLevelAsymmetryAllowed, "1");
+    constrained_high.SetParam(cricket::kH264FmtpPacketizationMode, "1");
+    supported_codecs_.push_back(constrained_high);
+  }
+
+  cricket::VideoCodec constrained_baseline(cricket::kH264CodecName);
+  const H264::ProfileLevelId constrained_baseline_profile(
+      H264::kProfileConstrainedBaseline, level);
+  constrained_baseline.SetParam(
+      cricket::kH264FmtpProfileLevelId,
+      *H264::ProfileLevelIdToString(constrained_baseline_profile));
+  constrained_baseline.SetParam(cricket::kH264FmtpLevelAsymmetryAllowed, "1");
+  constrained_baseline.SetParam(cricket::kH264FmtpPacketizationMode, "1");
+  supported_codecs_.push_back(constrained_baseline);
+
   return supported_codecs_;
 }
 
diff --git a/webrtc/sdk/objc/Framework/Classes/videotoolboxvideocodecfactory.h b/webrtc/sdk/objc/Framework/Classes/videotoolboxvideocodecfactory.h
index 5100710..8acd9dd 100644
--- a/webrtc/sdk/objc/Framework/Classes/videotoolboxvideocodecfactory.h
+++ b/webrtc/sdk/objc/Framework/Classes/videotoolboxvideocodecfactory.h
@@ -28,7 +28,9 @@
   const std::vector<cricket::VideoCodec>& supported_codecs() const override;
 
  private:
-  std::vector<cricket::VideoCodec> supported_codecs_;
+  // TODO(magjed): Mutable because it depends on a field trial and it is
+  // recalculated every call to supported_codecs().
+  mutable std::vector<cricket::VideoCodec> supported_codecs_;
 };
 
 class VideoToolboxVideoDecoderFactory
diff --git a/webrtc/sdk/objc/Framework/Headers/WebRTC/RTCFieldTrials.h b/webrtc/sdk/objc/Framework/Headers/WebRTC/RTCFieldTrials.h
index ee99788..60c51d8 100644
--- a/webrtc/sdk/objc/Framework/Headers/WebRTC/RTCFieldTrials.h
+++ b/webrtc/sdk/objc/Framework/Headers/WebRTC/RTCFieldTrials.h
@@ -16,6 +16,7 @@
 RTC_EXTERN NSString * const kRTCFieldTrialAudioSendSideBweKey;
 RTC_EXTERN NSString * const kRTCFieldTrialFlexFec03Key;
 RTC_EXTERN NSString * const kRTCFieldTrialImprovedBitrateEstimateKey;
+RTC_EXTERN NSString * const kRTCFieldTrialH264HighProfileKey;
 
 /** The valid value for field trials above. */
 RTC_EXTERN NSString * const kRTCFieldTrialEnabledValue;