diff --git a/media/engine/webrtcvideoengine_unittest.cc b/media/engine/webrtcvideoengine_unittest.cc
index 7b1eb4a583..2f3a2d2060 100644
--- a/media/engine/webrtcvideoengine_unittest.cc
+++ b/media/engine/webrtcvideoengine_unittest.cc
@@ -183,7 +183,7 @@ class WebRtcVideoEngineTest : public ::testing::Test {
  protected:
   // Find the index of the codec in the engine with the given name. The codec
   // must be present.
-  int GetEngineCodecIndex(const std::string& name) const;
+  size_t GetEngineCodecIndex(const std::string& name) const;
 
   // Find the codec in the engine with the given name. The codec must be
   // present.
@@ -569,7 +569,8 @@ TEST_F(WebRtcVideoEngineTest, PropagatesInputFrameTimestamp) {
   EXPECT_TRUE(channel->RemoveSendStream(kSsrc));
 }
 
-int WebRtcVideoEngineTest::GetEngineCodecIndex(const std::string& name) const {
+size_t WebRtcVideoEngineTest::GetEngineCodecIndex(
+    const std::string& name) const {
   const std::vector<cricket::VideoCodec> codecs = engine_.codecs();
   for (size_t i = 0; i < codecs.size(); ++i) {
     const cricket::VideoCodec engine_codec = codecs[i];
@@ -812,8 +813,8 @@ TEST_F(WebRtcVideoEngineTest, ReportSupportedExternalCodecs) {
   encoder_factory_->AddSupportedVideoCodecType(kFakeExternalCodecName);
 
   // The external codec should appear after the internal codec in the vector.
-  const int vp8_index = GetEngineCodecIndex("VP8");
-  const int fake_external_codec_index =
+  const size_t vp8_index = GetEngineCodecIndex("VP8");
+  const size_t fake_external_codec_index =
       GetEngineCodecIndex(kFakeExternalCodecName);
   EXPECT_LT(vp8_index, fake_external_codec_index);
 }
@@ -836,8 +837,8 @@ TEST_F(WebRtcVideoEngineTest, ReportSupportedExternalCodecsWithAddedCodec) {
 
   // Check that both fake codecs are present and that the second fake codec
   // appears after the first fake codec.
-  const int fake_codec_index1 = GetEngineCodecIndex(kFakeExternalCodecName1);
-  const int fake_codec_index2 = GetEngineCodecIndex(kFakeExternalCodecName2);
+  const size_t fake_codec_index1 = GetEngineCodecIndex(kFakeExternalCodecName1);
+  const size_t fake_codec_index2 = GetEngineCodecIndex(kFakeExternalCodecName2);
   EXPECT_LT(fake_codec_index1, fake_codec_index2);
 }
 
diff --git a/modules/congestion_controller/acknowledged_bitrate_estimator.cc b/modules/congestion_controller/acknowledged_bitrate_estimator.cc
index c0161ea0d9..1e75ee6e92 100644
--- a/modules/congestion_controller/acknowledged_bitrate_estimator.cc
+++ b/modules/congestion_controller/acknowledged_bitrate_estimator.cc
@@ -13,6 +13,7 @@
 #include <utility>
 
 #include "modules/rtp_rtcp/include/rtp_rtcp_defines.h"
+#include "rtc_base/numerics/safe_conversions.h"
 #include "rtc_base/ptr_util.h"
 
 namespace webrtc {
@@ -38,7 +39,8 @@ void AcknowledgedBitrateEstimator::IncomingPacketFeedbackVector(
   for (const auto& packet : packet_feedback_vector) {
     if (IsInSendTimeHistory(packet)) {
       MaybeExpectFastRateChange(packet.send_time_ms);
-      bitrate_estimator_->Update(packet.arrival_time_ms, packet.payload_size);
+      bitrate_estimator_->Update(packet.arrival_time_ms,
+                                 rtc::dchecked_cast<int>(packet.payload_size));
     }
   }
 }
diff --git a/modules/congestion_controller/probe_bitrate_estimator.cc b/modules/congestion_controller/probe_bitrate_estimator.cc
index 1a438829b1..8c754d789c 100644
--- a/modules/congestion_controller/probe_bitrate_estimator.cc
+++ b/modules/congestion_controller/probe_bitrate_estimator.cc
@@ -17,6 +17,7 @@
 #include "logging/rtc_event_log/rtc_event_log.h"
 #include "rtc_base/checks.h"
 #include "rtc_base/logging.h"
+#include "rtc_base/numerics/safe_conversions.h"
 #include "rtc_base/ptr_util.h"
 
 namespace {
@@ -65,7 +66,8 @@ int ProbeBitrateEstimator::HandleProbeAndEstimateBitrate(
 
   EraseOldClusters(packet_feedback.arrival_time_ms - kMaxClusterHistoryMs);
 
-  int payload_size_bits = packet_feedback.payload_size * 8;
+  int payload_size_bits = rtc::dchecked_cast<int>(
+      packet_feedback.payload_size * 8);
   AggregatedCluster* cluster = &clusters_[cluster_id];
 
   if (packet_feedback.send_time_ms < cluster->first_send_ms) {
diff --git a/modules/congestion_controller/send_side_congestion_controller.cc b/modules/congestion_controller/send_side_congestion_controller.cc
index ccca692712..2aeed51a01 100644
--- a/modules/congestion_controller/send_side_congestion_controller.cc
+++ b/modules/congestion_controller/send_side_congestion_controller.cc
@@ -22,6 +22,7 @@
 #include "rtc_base/checks.h"
 #include "rtc_base/format_macros.h"
 #include "rtc_base/logging.h"
+#include "rtc_base/numerics/safe_conversions.h"
 #include "rtc_base/ptr_util.h"
 #include "rtc_base/rate_limiter.h"
 #include "rtc_base/socket.h"
@@ -258,7 +259,7 @@ void SendSideCongestionController::SignalNetworkState(NetworkState state) {
 void SendSideCongestionController::SetTransportOverhead(
     size_t transport_overhead_bytes_per_packet) {
   transport_feedback_adapter_.SetTransportOverhead(
-      transport_overhead_bytes_per_packet);
+      rtc::dchecked_cast<int>(transport_overhead_bytes_per_packet));
 }
 
 void SendSideCongestionController::OnSentPacket(
diff --git a/p2p/base/relayserver.cc b/p2p/base/relayserver.cc
index a147904467..9bb53ad45a 100644
--- a/p2p/base/relayserver.cc
+++ b/p2p/base/relayserver.cc
@@ -21,6 +21,7 @@
 #include "rtc_base/checks.h"
 #include "rtc_base/helpers.h"
 #include "rtc_base/logging.h"
+#include "rtc_base/numerics/safe_conversions.h"
 #include "rtc_base/socketadapters.h"
 
 namespace cricket {
@@ -429,7 +430,8 @@ void RelayServer::HandleStunAllocate(
   response.AddAttribute(std::move(magic_cookie_attr));
 
   RTC_DCHECK_GT(external_sockets_.size(), 0);
-  size_t index = random_.Rand(external_sockets_.size() - 1);
+  size_t index = random_.Rand(rtc::dchecked_cast<uint32_t>(
+      external_sockets_.size() - 1));
   rtc::SocketAddress ext_addr =
       external_sockets_[index]->GetLocalAddress();
 
diff --git a/tools_webrtc/mb/mb_config.pyl b/tools_webrtc/mb/mb_config.pyl
index 4ee4d5cf15..0231874472 100644
--- a/tools_webrtc/mb/mb_config.pyl
+++ b/tools_webrtc/mb/mb_config.pyl
@@ -64,17 +64,18 @@
       'Android32 Builder MIPS (dbg)': 'android_debug_static_bot_mipsel',
 
       # Windows
-      'Win32 Debug': 'debug_bot_x86',
-      'Win32 Release': 'release_bot_x86',
-      'Win64 Debug': 'debug_bot_x64',
-      'Win64 Release': 'release_bot_x64',
+      'Win32 Debug': 'win_msvc_debug_bot_x86',
+      'Win32 Release': 'win_msvc_release_bot_x86',
+      'Win64 Debug': 'win_msvc_debug_bot_x64',
+      'Win64 Release': 'win_msvc_release_bot_x64',
       'Win32 Debug (Clang)': 'win_clang_debug_bot_x86',
       'Win32 Release (Clang)': 'win_clang_release_bot_x86',
       'Win64 Debug (Clang)': 'win_clang_debug_bot_x64',
       'Win64 Release (Clang)': 'win_clang_release_bot_x64',
       'Win32 ASan': 'win_asan_clang_release_bot_x86',
-      'Win32 Release (MSVC)': 'win_msvc_release_bot_x86',
       'Win32 Release [large tests]': 'release_bot_x86',
+      # TODO(bugs.webrtc.org/757293): remove this duplicate:
+      'Win32 Release (MSVC)': 'win_msvc_release_bot_x86',
     },
     'client.webrtc.branches': {
       # iOS
@@ -200,20 +201,21 @@
       'win_compile_rel': 'release_bot_x86',
       'win_compile_x64_dbg': 'debug_bot_x64',
       'win_compile_x64_rel': 'release_bot_x64',
-      'win_dbg': 'debug_bot_x86',
-      'win_rel': 'release_bot_x86',
-      'win_x64_dbg': 'debug_bot_x64',
-      'win_x64_rel': 'release_bot_x64',
+      'win_dbg': 'win_msvc_debug_bot_x86',
+      'win_rel': 'win_msvc_release_bot_x86',
+      'win_x64_dbg': 'win_msvc_debug_bot_x64',
+      'win_x64_rel': 'win_msvc_release_bot_x64',
       'win_clang_dbg': 'win_clang_debug_bot_x86',
       'win_clang_rel': 'win_clang_release_bot_x86',
       'win_x64_clang_dbg': 'win_clang_debug_bot_x64',
       'win_x64_clang_rel': 'win_clang_release_bot_x64',
       'win_asan': 'win_asan_clang_release_bot_x86',
-      'win_msvc_rel': 'win_msvc_release_bot_x86',
       'win_baremetal': 'release_bot_x86',
       'win_experimental': 'release_bot_x86',
       'win_x64_win8': 'debug_bot_x64',
       'win_x64_win10': 'debug_bot_x64',
+      # TODO(bugs.webrtc.org/757293): remove this duplicate:
+      'win_msvc_rel': 'win_msvc_release_bot_x86',
     }
   },
 
@@ -304,9 +306,18 @@
     'win_clang_release_bot_x64': [
       'gn', 'clang', 'openh264_release_bot', 'x64',
     ],
+    'win_msvc_debug_bot_x86': [
+      'gn', 'no_clang', 'openh264_debug_bot', 'x86',
+    ],
     'win_msvc_release_bot_x86': [
       'gn', 'no_clang', 'openh264_release_bot', 'x86',
     ],
+    'win_msvc_debug_bot_x64': [
+      'gn', 'no_clang', 'openh264_debug_bot', 'x64',
+    ],
+    'win_msvc_release_bot_x64': [
+      'gn', 'no_clang', 'openh264_release_bot', 'x64',
+    ],
     'win_asan_clang_release_bot_x86': [
       'gn', 'asan', 'clang',  'full_symbols', 'openh264_release_bot', 'x86',
       'win_fastlink',
@@ -378,6 +389,7 @@
       'gn_args': 'is_asan=true',
     },
 
+    # is_clang=true by default, this is only to guard from upstream changes.
     'clang': {
       'gn_args': 'is_clang=true',
     },
diff --git a/video/picture_id_tests.cc b/video/picture_id_tests.cc
index 22d1818db2..482f48823c 100644
--- a/video/picture_id_tests.cc
+++ b/video/picture_id_tests.cc
@@ -11,6 +11,7 @@
 #include "media/engine/simulcast_encoder_adapter.h"
 #include "modules/rtp_rtcp/source/rtp_format.h"
 #include "modules/video_coding/codecs/vp9/include/vp9.h"
+#include "rtc_base/numerics/safe_conversions.h"
 #include "rtc_base/numerics/sequence_number_util.h"
 #include "test/call_test.h"
 #include "test/field_trial.h"
@@ -277,8 +278,8 @@ class VideoStreamFactory
 
     // Use the same total bitrates when sending a single stream to avoid
     // lowering the bitrate estimate and requiring a subsequent rampup.
-    const int encoder_stream_bps =
-        kEncoderBitrateBps / encoder_config.number_of_streams;
+    const int encoder_stream_bps = kEncoderBitrateBps / rtc::checked_cast<int>(
+        encoder_config.number_of_streams);
 
     for (size_t i = 0; i < encoder_config.number_of_streams; ++i) {
       streams[i].min_bitrate_bps = encoder_stream_bps;