Add k prefix to FrameGenerator::OutputType enum values

This prepares for using VideoFrameBuffer::Type as
FrameGenerator::OutputType, which will reduce the
number of redundant enums in the code.

Bug: webrtc:9883
Change-Id: I253f5f1ea7181e02a5cf1a92925f51da8ada6aa2
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/146982
Reviewed-by: Erik Språng <sprang@webrtc.org>
Commit-Queue: Sebastian Jansson <srte@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#28696}
diff --git a/modules/video_coding/codecs/test/video_codec_unittest.cc b/modules/video_coding/codecs/test/video_codec_unittest.cc
index 6ebbb7c..4acfee2 100644
--- a/modules/video_coding/codecs/test/video_codec_unittest.cc
+++ b/modules/video_coding/codecs/test/video_codec_unittest.cc
@@ -75,7 +75,7 @@
 
   input_frame_generator_ = test::FrameGenerator::CreateSquareGenerator(
       codec_settings_.width, codec_settings_.height,
-      test::FrameGenerator::OutputType::I420, absl::optional<int>());
+      test::FrameGenerator::OutputType::kI420, absl::optional<int>());
 
   encoder_ = CreateEncoder();
   decoder_ = CreateDecoder();
diff --git a/modules/video_coding/codecs/vp8/test/vp8_impl_unittest.cc b/modules/video_coding/codecs/vp8/test/vp8_impl_unittest.cc
index a18e8ee..2dd2f46 100644
--- a/modules/video_coding/codecs/vp8/test/vp8_impl_unittest.cc
+++ b/modules/video_coding/codecs/vp8/test/vp8_impl_unittest.cc
@@ -491,7 +491,7 @@
   // details and high probability of overshoot.
   input_frame_generator_ = test::FrameGenerator::CreateSquareGenerator(
       codec_settings_.width, codec_settings_.height,
-      test::FrameGenerator::OutputType::I420,
+      test::FrameGenerator::OutputType::kI420,
       /* num_squares = */ absl::optional<int>(300));
 
   EXPECT_EQ(WEBRTC_VIDEO_CODEC_OK,
diff --git a/modules/video_coding/codecs/vp9/test/vp9_impl_unittest.cc b/modules/video_coding/codecs/vp9/test/vp9_impl_unittest.cc
index ae509a6..3ae1c06 100644
--- a/modules/video_coding/codecs/vp9/test/vp9_impl_unittest.cc
+++ b/modules/video_coding/codecs/vp9/test/vp9_impl_unittest.cc
@@ -1374,7 +1374,7 @@
     TestVp9Impl::SetUp();
     input_frame_generator_ = test::FrameGenerator::CreateSquareGenerator(
         codec_settings_.width, codec_settings_.height,
-        test::FrameGenerator::OutputType::I010, absl::optional<int>());
+        test::FrameGenerator::OutputType::kI010, absl::optional<int>());
   }
 
   std::unique_ptr<VideoEncoder> CreateEncoder() override {
diff --git a/test/frame_generator.cc b/test/frame_generator.cc
index 7a9e9a0..276069e 100644
--- a/test/frame_generator.cc
+++ b/test/frame_generator.cc
@@ -74,12 +74,12 @@
 
     rtc::scoped_refptr<VideoFrameBuffer> buffer = nullptr;
     switch (type_) {
-      case OutputType::I420:
-      case OutputType::I010: {
+      case OutputType::kI420:
+      case OutputType::kI010: {
         buffer = CreateI420Buffer(width_, height_);
         break;
       }
-      case OutputType::I420A: {
+      case OutputType::kI420A: {
         rtc::scoped_refptr<I420Buffer> yuv_buffer =
             CreateI420Buffer(width_, height_);
         rtc::scoped_refptr<I420Buffer> axx_buffer =
@@ -92,12 +92,14 @@
             rtc::Bind(&KeepBufferRefs, yuv_buffer, axx_buffer));
         break;
       }
+      default:
+        RTC_NOTREACHED() << "The given output format is not supported.";
     }
 
     for (const auto& square : squares_)
       square->Draw(buffer);
 
-    if (type_ == OutputType::I010) {
+    if (type_ == OutputType::kI010) {
       buffer = I010Buffer::Copy(*buffer->ToI420());
     }
 
@@ -519,7 +521,7 @@
     absl::optional<OutputType> type,
     absl::optional<int> num_squares) {
   return std::unique_ptr<FrameGenerator>(
-      new SquareGenerator(width, height, type.value_or(OutputType::I420),
+      new SquareGenerator(width, height, type.value_or(OutputType::kI420),
                           num_squares.value_or(10)));
 }
 
diff --git a/test/frame_generator.h b/test/frame_generator.h
index 358dc0f..31543bc 100644
--- a/test/frame_generator.h
+++ b/test/frame_generator.h
@@ -58,7 +58,13 @@
   // Change the capture resolution.
   virtual void ChangeResolution(size_t width, size_t height);
 
-  enum class OutputType { I420, I420A, I010 };
+  enum class OutputType {
+    kI420,
+    // TODO(srte): Remove alias when downstream is updated.
+    I420 = kI420,
+    kI420A,
+    kI010
+  };
 
   // Creates a frame generator that produces frames with small squares that
   // move randomly towards the lower right corner.
diff --git a/test/pc/e2e/peer_connection_quality_test.cc b/test/pc/e2e/peer_connection_quality_test.cc
index f7747bd..20ad73b 100644
--- a/test/pc/e2e/peer_connection_quality_test.cc
+++ b/test/pc/e2e/peer_connection_quality_test.cc
@@ -709,11 +709,11 @@
     absl::optional<test::FrameGenerator::OutputType> frame_generator_type =
         absl::nullopt;
     if (video_config.generator == VideoGeneratorType::kDefault) {
-      frame_generator_type = test::FrameGenerator::OutputType::I420;
+      frame_generator_type = test::FrameGenerator::OutputType::kI420;
     } else if (video_config.generator == VideoGeneratorType::kI420A) {
-      frame_generator_type = test::FrameGenerator::OutputType::I420A;
+      frame_generator_type = test::FrameGenerator::OutputType::kI420A;
     } else if (video_config.generator == VideoGeneratorType::kI010) {
-      frame_generator_type = test::FrameGenerator::OutputType::I010;
+      frame_generator_type = test::FrameGenerator::OutputType::kI010;
     }
     return test::FrameGenerator::CreateSquareGenerator(
         static_cast<int>(video_config.width),
diff --git a/test/scenario/scenario_config.h b/test/scenario/scenario_config.h
index bd9cb55..13d85c3 100644
--- a/test/scenario/scenario_config.h
+++ b/test/scenario/scenario_config.h
@@ -103,7 +103,7 @@
     } slides;
     struct Generator {
       using PixelFormat = FrameGenerator::OutputType;
-      PixelFormat pixel_format = PixelFormat::I420;
+      PixelFormat pixel_format = PixelFormat::kI420;
       int width = 320;
       int height = 180;
     } generator;
diff --git a/video/video_quality_test.cc b/video/video_quality_test.cc
index 535c5e9..fedcffa 100644
--- a/video/video_quality_test.cc
+++ b/video/video_quality_test.cc
@@ -1120,12 +1120,12 @@
       frame_generator = test::FrameGenerator::CreateSquareGenerator(
           static_cast<int>(params_.video[video_idx].width),
           static_cast<int>(params_.video[video_idx].height),
-          test::FrameGenerator::OutputType::I420A, absl::nullopt);
+          test::FrameGenerator::OutputType::kI420A, absl::nullopt);
     } else if (params_.video[video_idx].clip_path == "GeneratorI010") {
       frame_generator = test::FrameGenerator::CreateSquareGenerator(
           static_cast<int>(params_.video[video_idx].width),
           static_cast<int>(params_.video[video_idx].height),
-          test::FrameGenerator::OutputType::I010, absl::nullopt);
+          test::FrameGenerator::OutputType::kI010, absl::nullopt);
     } else if (params_.video[video_idx].clip_path.empty()) {
       video_sources_[video_idx] = test::CreateVideoCapturer(
           params_.video[video_idx].width, params_.video[video_idx].height,