Example failures:

https://build.chromium.org/p/chromium.webrtc/builders/Mac%20Tester/builds/65714/steps/content_browsertests/
[ RUN      ] WebRtcCaptureFromElementBrowserTest.VerifyCanvasCaptureOffscreenCanvasCommitFrames
[4540:779:0223/055729.272997:285916762377:ERROR:gl_surface.cc(137)] Not implemented reached in virtual gl::GLSurfaceFormat gl::GLSurface::GetFormat()
[4540:779:0223/055729.273106:285916865736:ERROR:gl_surface.cc(137)] Not implemented reached in virtual gl::GLSurfaceFormat gl::GLSurface::GetFormat()
[4540:779:0223/055729.286289:285930051085:ERROR:gl_surface.cc(137)] Not implemented reached in virtual gl::GLSurfaceFormat gl::GLSurface::GetFormat()
[4540:779:0223/055729.286334:285930093137:ERROR:gl_surface.cc(137)] Not implemented reached in virtual gl::GLSurfaceFormat gl::GLSurface::GetFormat()
[4540:779:0223/055729.288009:285931770009:ERROR:gl_surface.cc(137)] Not implemented reached in virtual gl::GLSurfaceFormat gl::GLSurface::GetFormat()
[4540:779:0223/055729.288061:285931822692:ERROR:gl_surface.cc(137)] Not implemented reached in virtual gl::GLSurfaceFormat gl::GLSurface::GetFormat()
[4540:779:0223/055729.332603:285976365524:ERROR:gl_surface.cc(137)] Not implemented reached in virtual gl::GLSurfaceFormat gl::GLSurface::GetFormat()
[4540:779:0223/055729.332657:285976416610:ERROR:gl_surface.cc(137)] Not implemented reached in virtual gl::GLSurfaceFormat gl::GLSurface::GetFormat()
[4540:779:0223/055729.337755:285981517414:ERROR:gl_surface.cc(137)] Not implemented reached in virtual gl::GLSurfaceFormat gl::GLSurface::GetFormat()
[4540:779:0223/055729.337816:285981577249:ERROR:gl_surface.cc(137)] Not implemented reached in virtual gl::GLSurfaceFormat gl::GLSurface::GetFormat()
[OpenH264] this = 0x0x7fc640d63ed0, Info:CWelsH264SVCEncoder::InitEncoder(), openh264 codec version = openh264 default: 1.4
[OpenH264] this = 0x0x7fc640d63ed0, Info:iUsageType = 0,iPicWidth= 64;iPicHeight= 64;iTargetBitrate= 0;iMaxBitrate= 0;iRCMode= -1;iPaddingFlag= 0;iTemporalLayerNum= 1;iSpatialLayerNum= 1;fFrameRate= 60.000000f;uiIntraPeriod= 100;eSpsPpsIdStrategy = 1;bPrefixNalAddingCtrl = 0;bSimulcastAVC=0;bEnableDenoise= 0;bEnableBackgroundDetection= 1;bEnableSceneChangeDetect = 1;bEnableAdaptiveQuant= 1;bEnableFrameSkip= 1;bEnableLongTermReference= 0;iLtrMarkPeriod= 30;iComplexityMode = 1;iNumRefFrame = 1;iEntropyCodingModeFlag = 0;uiMaxNalSize = 0;iLTRRefNum = 0;iMultipleThreadIdc = 1;iLoopFilterDisableIdc = 0 (offset(alpha/beta): 0,0;iMaxQp = 51;iMinQp = 0)
[OpenH264] this = 0x0x7fc640d63ed0, Info:sSpatialLayers[0]: .iVideoWidth= 64; .iVideoHeight= 64; .fFrameRate= 60.000000f; .iSpatialBitrate= 0; .iMaxSpatialBitrate= 0; .sSliceArgument.uiSliceMode= 1; .sSliceArgument.iSliceNum= 1; .sSliceArgument.uiSliceSizeConstraint= 1500;uiProfileIdc = 66;uiLevelIdc = 0
[OpenH264] this = 0x0x7fc640d63ed0, Info:SliceArgumentValidationFixedSliceMode(), uiSliceNum(1) you set for SM_FIXEDSLCNUM_SLICE, now turn to SM_SINGLE_SLICE type!
[OpenH264] this = 0x0x7fc640d63ed0, Info:SliceArgumentValidationFixedSliceMode(), uiSliceNum(1) you set for SM_FIXEDSLCNUM_SLICE, now turn to SM_SINGLE_SLICE type as CountMbNum less than MIN_NUM_MB_PER_SLICE!
[OpenH264] this = 0x0x7fc640c4c3c0, Info:CWelsH264SVCEncoder::InitEncoder(), openh264 codec version = openh264 default: 1.4
[OpenH264] this = 0x0x7fc640c4c3c0, Info:iUsageType = 0,iPicWidth= 64;iPicHeight= 64;iTargetBitrate= 0;iMaxBitrate= 0;iRCMode= -1;iPaddingFlag= 0;iTemporalLayerNum= 1;iSpatialLayerNum= 1;fFrameRate= 60.000000f;uiIntraPeriod= 100;eSpsPpsIdStrategy = 1;bPrefixNalAddingCtrl = 0;bSimulcastAVC=0;bEnableDenoise= 0;bEnableBackgroundDetection= 1;bEnableSceneChangeDetect = 1;bEnableAdaptiveQuant= 1;bEnableFrameSkip= 1;bEnableLongTermReference= 0;iLtrMarkPeriod= 30;iComplexityMode = 1;iNumRefFrame = 1;iEntropyCodingModeFlag = 0;uiMaxNalSize = 0;iLTRRefNum = 0;iMultipleThreadIdc = 1;iLoopFilterDisableIdc = 0 (offset(alpha/beta): 0,0;iMaxQp = 51;iMinQp = 0)
[OpenH264] this = 0x0x7fc640c4c3c0, Info:sSpatialLayers[0]: .iVideoWidth= 64; .iVideoHeight= 64; .fFrameRate= 60.000000f; .iSpatialBitrate= 0; .iMaxSpatialBitrate= 0; .sSliceArgument.uiSliceMode= 1; .sSliceArgument.iSliceNum= 1; .sSliceArgument.uiSliceSizeConstraint= 1500;uiProfileIdc = 66;uiLevelIdc = 0
[OpenH264] this = 0x0x7fc640c4c3c0, Info:SliceArgumentValidationFixedSliceMode(), uiSliceNum(1) you set for SM_FIXEDSLCNUM_SLICE, now turn to SM_SINGLE_SLICE type!
[OpenH264] this = 0x0x7fc640c4c3c0, Info:SliceArgumentValidationFixedSliceMode(), uiSliceNum(1) you set for SM_FIXEDSLCNUM_SLICE, now turn to SM_SINGLE_SLICE type as CountMbNum less than MIN_NUM_MB_PER_SLICE!
[OpenH264] this = 0x0x7fc640d63ed0, Info:WelsInitEncoderExt() exit, overall memory usage: 369354 bytes
[OpenH264] this = 0x0x7fc640d63ed0, Info:CWelsH264SVCEncoder::SetOption():ENCODER_OPTION_DATAFORMAT, m_iCspInternal= 0x17
[OpenH264] this = 0x0x7fc640c4c3c0, Info:WelsInitEncoderExt() exit, overall memory usage: 369354 bytes
[OpenH264] this = 0x0x7fc640c4c3c0, Info:CWelsH264SVCEncoder::SetOption():ENCODER_OPTION_DATAFORMAT, m_iCspInternal= 0x17
[OpenH264] this = 0x0x7fc640d63ed0, Info:CWelsH264SVCEncoder::Uninitialize(), openh264 codec version = openh264 default: 1.4.
[OpenH264] this = 0x0x7fc640d63ed0, Info:WelsUninitEncoderExt(), pCtx= 0x7fc6418e0a00, iMultipleThreadIdc= 1.
[OpenH264] this = 0x0x7fc640d63ed0, Info:FreeMemorySvc(), verify memory usage (0 bytes) after free..
[OpenH264] this = 0x0x7fc640d63ed0, Info:CWelsH264SVCEncoder::~CWelsH264SVCEncoder()
[4540:779:0223/055729.411862:286055625085:ERROR:gles2_cmd_decoder.cc(17363)] [.DisplayCompositor-0x7f832b83b000]GL ERROR :GL_INVALID_OPERATION : glCreateAndConsumeTextureCHROMIUM: invalid mailbox name
[4540:779:0223/055729.415188:286058950071:ERROR:gles2_cmd_decoder.cc(9597)] [.DisplayCompositor-0x7f832b83b000]RENDER WARNING: texture bound to texture unit 0 is not renderable. It maybe non-power-of-2 and have incompatible texture filtering.
[4540:779:0223/055729.445401:286089164553:ERROR:texture_manager.cc(2119)] [.DisplayCompositor-0x7f832b83b000]GL ERROR :GL_INVALID_ENUM : glTexParameteri: param was GL_FALSE
[4540:779:0223/055729.445469:286089231858:ERROR:texture_manager.cc(2119)] [.DisplayCompositor-0x7f832b83b000]GL ERROR :GL_INVALID_ENUM : glTexParameteri: param was GL_FALSE
[4540:779:0223/055729.454478:286098240453:ERROR:texture_manager.cc(2119)] [.DisplayCompositor-0x7f832b83b000]GL ERROR :GL_INVALID_ENUM : glTexParameteri: param was GL_FALSE
[4540:779:0223/055729.454535:286098295142:ERROR:texture_manager.cc(2119)] [.DisplayCompositor-0x7f832b83b000]GL ERROR :GL_INVALID_ENUM : glTexParameteri: param was GL_FALSE
[4540:779:0223/055729.455017:286098778563:ERROR:gles2_cmd_decoder.cc(17363)] [.DisplayCompositor-0x7f832b83b000]GL ERROR :GL_INVALID_OPERATION : glCreateAndConsumeTextureCHROMIUM: invalid mailbox name
[4540:779:0223/055729.455082:286098843388:ERROR:gles2_cmd_decoder.cc(9597)] [.DisplayCompositor-0x7f832b83b000]RENDER WARNING: texture bound to texture unit 0 is not renderable. It maybe non-power-of-2 and have incompatible texture filtering.
[4540:779:0223/055729.472043:286115807852:ERROR:texture_manager.cc(2119)] [.DisplayCompositor-0x7f832b83b000]GL ERROR :GL_INVALID_ENUM : glTexParameteri: param was GL_FALSE
[4540:779:0223/055729.472116:286115878698:ERROR:texture_manager.cc(2119)] [.DisplayCompositor-0x7f832b83b000]GL ERROR :GL_INVALID_ENUM : glTexParameteri: param was GL_FALSE
[4540:779:0223/055729.472542:286116304078:ERROR:gles2_cmd_decoder.cc(17363)] [.DisplayCompositor-0x7f832b83b000]GL ERROR :GL_INVALID_OPERATION : glCreateAndConsumeTextureCHROMIUM: invalid mailbox name
[4540:779:0223/055729.472622:286116383171:ERROR:gles2_cmd_decoder.cc(9597)] [.DisplayCompositor-0x7f832b83b000]RENDER WARNING: texture bound to texture unit 0 is not renderable. It maybe non-power-of-2 and have incompatible texture filtering.
[4540:779:0223/055729.488351:286132113940:ERROR:texture_manager.cc(2119)] [.DisplayCompositor-0x7f832b83b000]GL ERROR :GL_INVALID_ENUM : glTexParameteri: param was GL_FALSE
[4540:779:0223/055729.488444:286132206019:ERROR:texture_manager.cc(2119)] [.DisplayCompositor-0x7f832b83b000]GL ERROR :GL_INVALID_ENUM : glTexParameteri: param was GL_FALSE
[4540:779:0223/055729.488926:286132686872:ERROR:gles2_cmd_decoder.cc(17363)] [.DisplayCompositor-0x7f832b83b000]GL ERROR :GL_INVALID_OPERATION : glCreateAndConsumeTextureCHROMIUM: invalid mailbox name
[4540:779:0223/055729.488977:286132737026:ERROR:gles2_cmd_decoder.cc(9597)] [.DisplayCompositor-0x7f832b83b000]RENDER WARNING: texture bound to texture unit 0 is not renderable. It maybe non-power-of-2 and have incompatible texture filtering.
[4540:779:0223/055729.505309:286149071955:ERROR:texture_manager.cc(2119)] [.DisplayCompositor-0x7f832b83b000]GL ERROR :GL_INVALID_ENUM : glTexParameteri: param was GL_FALSE
[4540:779:0223/055729.505368:286149130011:ERROR:texture_manager.cc(2119)] [.DisplayCompositor-0x7f832b83b000]GL ERROR :GL_INVALID_ENUM : glTexParameteri: param was GL_FALSE
[4540:779:0223/055729.505809:286149570558:ERROR:gles2_cmd_decoder.cc(17363)] [.DisplayCompositor-0x7f832b83b000]GL ERROR :GL_INVALID_OPERATION : glCreateAndConsumeTextureCHROMIUM: invalid mailbox name
[4540:779:0223/055729.505877:286149638568:ERROR:gles2_cmd_decoder.cc(9597)] [.DisplayCompositor-0x7f832b83b000]RENDER WARNING: texture bound to texture unit 0 is not renderable. It maybe non-power-of-2 and have incompatible texture filtering.
[4540:779:0223/055729.522088:286165850364:ERROR:texture_manager.cc(2119)] [.DisplayCompositor-0x7f832b83b000]GL ERROR :GL_INVALID_ENUM : glTexParameteri: param was GL_FALSE
[4540:779:0223/055729.522141:286165900756:ERROR:texture_manager.cc(2119)] [.DisplayCompositor-0x7f832b83b000]GL ERROR :GL_INVALID_ENUM : glTexParameteri: param was GL_FALSE
[4540:779:0223/055729.522698:286166459602:ERROR:gles2_cmd_decoder.cc(17363)] [.DisplayCompositor-0x7f832b83b000]GL ERROR :GL_INVALID_OPERATION : glCreateAndConsumeTextureCHROMIUM: invalid mailbox name
[4540:779:0223/055729.522764:286166526303:ERROR:gles2_cmd_decoder.cc(9597)] [.DisplayCompositor-0x7f832b83b000]RENDER WARNING: texture bound to texture unit 0 is not renderable. It maybe non-power-of-2 and have incompatible texture filtering.
[4540:779:0223/055729.540361:286184129707:ERROR:texture_manager.cc(2119)] [.DisplayCompositor-0x7f832b83b000]GL ERROR :GL_INVALID_ENUM : glTexParameteri: param was GL_FALSE
[4540:779:0223/055729.540456:286184218361:ERROR:texture_manager.cc(2119)] [.DisplayCompositor-0x7f832b83b000]GL ERROR :GL_INVALID_ENUM : glTexParameteri: param was GL_FALSE
[4540:779:0223/055729.541021:286184783896:ERROR:gles2_cmd_decoder.cc(17363)] [.DisplayCompositor-0x7f832b83b000]GL ERROR :GL_INVALID_OPERATION : glCreateAndConsumeTextureCHROMIUM: invalid mailbox name
[4540:779:0223/055729.541101:286184862325:ERROR:gles2_cmd_decoder.cc(9597)] [.DisplayCompositor-0x7f832b83b000]RENDER WARNING: texture bound to texture unit 0 is not renderable. It maybe non-power-of-2 and have incompatible texture filtering.
[4540:779:0223/055729.556075:286199839786:ERROR:texture_manager.cc(2119)] [.DisplayCompositor-0x7f832b83b000]GL ERROR :GL_INVALID_ENUM : glTexParameteri: param was GL_FALSE
[4540:779:0223/055729.556149:286199909560:ERROR:texture_manager.cc(2119)] [.DisplayCompositor-0x7f832b83b000]GL ERROR :GL_INVALID_ENUM : glTexParameteri: param was GL_FALSE
[4540:779:0223/055729.556785:286200548108:ERROR:gles2_cmd_decoder.cc(17363)] [.DisplayCompositor-0x7f832b83b000]GL ERROR :GL_INVALID_OPERATION : glCreateAndConsumeTextureCHROMIUM: invalid mailbox name
[4540:779:0223/055729.556863:286200624025:ERROR:gles2_cmd_decoder.cc(9597)] [.DisplayCompositor-0x7f832b83b000]RENDER WARNING: texture bound to texture unit 0 is not renderable. It maybe non-power-of-2 and have incompatible texture filtering.
[4540:779:0223/055729.572723:286216494949:ERROR:texture_manager.cc(2119)] [.DisplayCompositor-0x7f832b83b000]GL ERROR :GL_INVALID_ENUM : glTexParameteri: param was GL_FALSE
[4540:779:0223/055729.572837:286216603278:ERROR:texture_manager.cc(2119)] [.DisplayCompositor-0x7f832b83b000]GL ERROR :GL_INVALID_ENUM : glTexParameteri: param was GL_FALSE
[4540:779:0223/055729.573599:286217362116:ERROR:gles2_cmd_decoder.cc(17363)] [.DisplayCompositor-0x7f832b83b000]GL ERROR :GL_INVALID_OPERATION : glCreateAndConsumeTextureCHROMIUM: invalid mailbox name
[4540:779:0223/055729.573705:286217466602:ERROR:gles2_cmd_decoder.cc(9597)] [.DisplayCompositor-0x7f832b83b000]RENDER WARNING: texture bound to texture unit 0 is not renderable. It maybe non-power-of-2 and have incompatible texture filtering.
[4540:779:0223/055729.589401:286233168624:ERROR:texture_manager.cc(2119)] [.DisplayCompositor-0x7f832b83b000]GL ERROR :GL_INVALID_ENUM : glTexParameteri: param was GL_FALSE
[4540:779:0223/055729.589494:286233255805:ERROR:texture_manager.cc(2119)] [.DisplayCompositor-0x7f832b83b000]GL ERROR :GL_INVALID_ENUM : glTexParameteri: param was GL_FALSE
[4540:779:0223/055729.590169:286233931917:ERROR:gles2_cmd_decoder.cc(17363)] [.DisplayCompositor-0x7f832b83b000]GL ERROR :GL_INVALID_OPERATION : glCreateAndConsumeTextureCHROMIUM: invalid mailbox name
[4540:779:0223/055729.590247:286234008411:ERROR:gles2_cmd_decoder.cc(9597)] [.DisplayCompositor-0x7f832b83b000]RENDER WARNING: texture bound to texture unit 0 is not renderable. It maybe non-power-of-2 and have incompatible texture filtering.
[4539:779:0223/055729.596568:286240335580:INFO:CONSOLE(29)] "Test Success", source: http://127.0.0.1:49994/media/webrtc_test_utilities.js (29)
[4540:779:0223/055729.602103:286245897438:ERROR:texture_manager.cc(2119)] [.DisplayCompositor-0x7f832b83b000]GL ERROR :GL_INVALID_ENUM : glTexParameteri: param was GL_FALSE
[4540:779:0223/055729.602156:286245946751:ERROR:texture_manager.cc(2119)] [.DisplayCompositor-0x7f832b83b000]GL ERROR :GL_INVALID_ENUM : glTexParameteri: param was GL_FALSE
[OpenH264] this = 0x0x7fc640c4c3c0, Info:CWelsH264SVCEncoder::Uninitialize(), openh264 codec version = openh264 default: 1.4.
[OpenH264] this = 0x0x7fc640c4c3c0, Info:WelsUninitEncoderExt(), pCtx= 0x7fc641047c00, iMultipleThreadIdc= 1.
[OpenH264] this = 0x0x7fc640c4c3c0, Info:FreeMemorySvc(), verify memory usage (0 bytes) after free..
[OpenH264] this = 0x0x7fc640c4c3c0, Info:CWelsH264SVCEncoder::~CWelsH264SVCEncoder()
[4539:779:0223/055729.637194:286280987958:FATAL:surface_manager.cc(71)] Check failed: frame_sink_source_map_.size() == 0u (1 vs. 0)
0   content_browsertests                0x000000010b379e6c base::debug::StackTrace::StackTrace(unsigned long) + 28
1   content_browsertests                0x000000010b39f513 logging::LogMessage::~LogMessage() + 67
2   content_browsertests                0x000000010c9558e6 cc::SurfaceManager::~SurfaceManager() + 550
3   content_browsertests                0x0000000109ea2b7a content::GpuProcessTransportFactory::~GpuProcessTransportFactory() + 522
4   content_browsertests                0x0000000109ea2be5 non-virtual thunk to content::GpuProcessTransportFactory::~GpuProcessTransportFactory() + 21
5   content_browsertests                0x0000000109ea84b8 content::ImageTransportFactory::Terminate() + 24
6   content_browsertests                0x0000000109953cdb content::BrowserMainLoop::ShutdownThreadsAndCleanUp() + 763
7   content_browsertests                0x0000000109957346 content::BrowserMainRunnerImpl::Shutdown() + 566
8   content_browsertests                0x000000010aea965c ShellBrowserMain(content::MainFunctionParams const&, std::__1::unique_ptr<content::BrowserMainRunner, std::__1::default_delete<content::BrowserMainRunner> > const&) + 172
9   content_browsertests                0x000000010ae68807 content::ShellMainDelegate::RunProcess(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&, content::MainFunctionParams const&) + 167
10  content_browsertests                0x00000001098290dd content::RunNamedProcessTypeMain(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&, content::MainFunctionParams const&, content::ContentMainDelegate*) + 781
11  content_browsertests                0x0000000109829990 content::ContentMainRunnerImpl::Run() + 528
12  content_browsertests                0x0000000109828a96 content::ContentMain(content::ContentMainParams const&) + 54
13  content_browsertests                0x000000010adf569d content::BrowserTestBase::SetUp() + 2301
14  content_browsertests                0x000000010ade364f content::ContentBrowserTest::SetUp() + 735
15  content_browsertests                0x000000010b14e041 testing::Test::Run() + 97
16  content_browsertests                0x000000010b14ebe0 testing::TestInfo::Run() + 288
17  content_browsertests                0x000000010b14f237 testing::TestCase::Run() + 263
18  content_browsertests                0x000000010b156267 testing::internal::UnitTestImpl::RunAllTests() + 871
19  content_browsertests                0x000000010b155ed3 testing::UnitTest::Run() + 163
20  content_browsertests                0x000000010ae3c5b5 base::TestSuite::Run() + 133
21  content_browsertests                0x000000010ade7dba content::ContentTestLauncherDelegate::RunTestSuite(int, char**) + 42
22  content_browsertests                0x000000010ae1ac62 content::LaunchTests(content::TestLauncherDelegate*, int, int, char**) + 386
23  content_browsertests                0x000000010ade7d5a main + 74
24  libdyld.dylib                       0x00007fff867bd5c9 start + 1
25  ???                                 0x0000000000000009 0x0 + 9

Further failures in https://build.chromium.org/p/chromium.webrtc/builders/Mac%20Tester?numbuilds=200.

Emircan PTAL.