diff --git a/browser_patches/checkout_build_archive_upload.sh b/browser_patches/checkout_build_archive_upload.sh
index 47b7627872..c126a3a41f 100755
--- a/browser_patches/checkout_build_archive_upload.sh
+++ b/browser_patches/checkout_build_archive_upload.sh
@@ -33,15 +33,25 @@ fi
 
 BROWSER_NAME=""
 EXTRA_BUILD_ARGS=""
+EXTRA_ARCHIVE_ARGS=""
 BUILD_FLAVOR="$1"
 BUILD_BLOB_NAME=""
 EXPECTED_HOST_OS=""
 EXPECTED_HOST_OS_VERSION=""
 EXPECTED_ARCH="x86_64"
+
+# ===========================
+#    WINLDD COMPILATION
+# ===========================
 if [[ "$BUILD_FLAVOR" == "winldd-win64" ]]; then
   BROWSER_NAME="winldd"
   EXPECTED_HOST_OS="MINGW"
   BUILD_BLOB_NAME="winldd-win64.zip"
+
+
+# ===========================
+#    FFMPEG COMPILATION
+# ===========================
 elif [[ "$BUILD_FLAVOR" == "ffmpeg-mac" ]]; then
   BROWSER_NAME="ffmpeg"
   EXTRA_BUILD_ARGS="--mac"
@@ -66,58 +76,81 @@ elif [[ "$BUILD_FLAVOR" == "ffmpeg-cross-compile-win64" ]]; then
   EXPECTED_HOST_OS="Ubuntu"
   EXPECTED_HOST_OS_VERSION="20.04"
   BUILD_BLOB_NAME="ffmpeg-win64.zip"
+
+# ===========================
+#    CHROMIUM COMPILATION
+# ===========================
 elif [[ "$BUILD_FLAVOR" == "chromium-win32" ]]; then
   BROWSER_NAME="chromium"
   EXTRA_BUILD_ARGS="--compile-win32"
+  EXTRA_ARCHIVE_ARGS="--compile-win32"
   EXPECTED_HOST_OS="MINGW"
   BUILD_BLOB_NAME="chromium-win32.zip"
 elif [[ "$BUILD_FLAVOR" == "chromium-win64" ]]; then
   BROWSER_NAME="chromium"
   EXTRA_BUILD_ARGS="--compile-win64"
+  EXTRA_ARCHIVE_ARGS="--compile-win64"
   EXPECTED_HOST_OS="MINGW"
   BUILD_BLOB_NAME="chromium-win64.zip"
 elif [[ "$BUILD_FLAVOR" == "chromium-mac" ]]; then
   BROWSER_NAME="chromium"
   EXTRA_BUILD_ARGS="--compile-mac"
+  EXTRA_ARCHIVE_ARGS="--compile-mac"
   EXPECTED_HOST_OS="Darwin"
   EXPECTED_HOST_OS_VERSION="10.15"
   BUILD_BLOB_NAME="chromium-mac.zip"
 elif [[ "$BUILD_FLAVOR" == "chromium-mac-arm64" ]]; then
   BROWSER_NAME="chromium"
   EXTRA_BUILD_ARGS="--compile-mac-arm64"
+  EXTRA_ARCHIVE_ARGS="--compile-mac-arm64"
   EXPECTED_HOST_OS="Darwin"
   EXPECTED_HOST_OS_VERSION="10.15"
   BUILD_BLOB_NAME="chromium-mac-arm64.zip"
 elif [[ "$BUILD_FLAVOR" == "chromium-linux" ]]; then
   BROWSER_NAME="chromium"
   EXTRA_BUILD_ARGS="--compile-linux"
+  EXTRA_ARCHIVE_ARGS="--compile-linux"
   EXPECTED_HOST_OS="Ubuntu"
   EXPECTED_HOST_OS_VERSION="18.04"
   BUILD_BLOB_NAME="chromium-linux.zip"
+
+
+# ===========================
+#    CHROMIUM MIRRORING
+# ===========================
 elif [[ "$BUILD_FLAVOR" == "chromium-linux-mirror-to-cdn" ]]; then
   BROWSER_NAME="chromium"
   EXTRA_BUILD_ARGS="--mirror-linux"
+  EXTRA_ARCHIVE_ARGS="--mirror-linux"
   EXPECTED_HOST_OS="Ubuntu"
   EXPECTED_HOST_OS_VERSION="18.04"
   BUILD_BLOB_NAME="chromium-linux.zip"
 elif [[ "$BUILD_FLAVOR" == "chromium-mac-mirror-to-cdn" ]]; then
   BROWSER_NAME="chromium"
   EXTRA_BUILD_ARGS="--mirror-mac"
+  EXTRA_ARCHIVE_ARGS="--mirror-mac"
   EXPECTED_HOST_OS="Ubuntu"
   EXPECTED_HOST_OS_VERSION="18.04"
   BUILD_BLOB_NAME="chromium-mac.zip"
 elif [[ "$BUILD_FLAVOR" == "chromium-win32-mirror-to-cdn" ]]; then
   BROWSER_NAME="chromium"
   EXTRA_BUILD_ARGS="--mirror-win32"
+  EXTRA_ARCHIVE_ARGS="--mirror-win32"
   EXPECTED_HOST_OS="Ubuntu"
   EXPECTED_HOST_OS_VERSION="18.04"
   BUILD_BLOB_NAME="chromium-win32.zip"
 elif [[ "$BUILD_FLAVOR" == "chromium-win64-mirror-to-cdn" ]]; then
   BROWSER_NAME="chromium"
   EXTRA_BUILD_ARGS="--mirror-win64"
+  EXTRA_ARCHIVE_ARGS="--mirror-win64"
   EXPECTED_HOST_OS="Ubuntu"
   EXPECTED_HOST_OS_VERSION="18.04"
   BUILD_BLOB_NAME="chromium-win64.zip"
+
+
+# ===========================
+#    FIREFOX COMPILATION
+# ===========================
 elif [[ "$BUILD_FLAVOR" == "firefox-ubuntu-18.04" ]]; then
   BROWSER_NAME="firefox"
   EXTRA_BUILD_ARGS="--full"
@@ -146,6 +179,11 @@ elif [[ "$BUILD_FLAVOR" == "firefox-win64" ]]; then
   EXTRA_BUILD_ARGS="--win64"
   EXPECTED_HOST_OS="MINGW"
   BUILD_BLOB_NAME="firefox-win64.zip"
+
+
+# ===========================
+#    WEBKIT COMPILATION
+# ===========================
 elif [[ "$BUILD_FLAVOR" == "webkit-ubuntu-18.04" ]]; then
   BROWSER_NAME="webkit"
   EXTRA_BUILD_ARGS="--full"
@@ -255,7 +293,7 @@ function generate_and_upload_browser_build {
   fi
 
   echo "-- archiving to $ZIP_PATH"
-  if ! ./$BROWSER_NAME/archive.sh $ZIP_PATH; then
+  if ! ./$BROWSER_NAME/archive.sh $ZIP_PATH "$EXTRA_ARCHIVE_ARGS"; then
     return 23
   fi
 
diff --git a/browser_patches/chromium/archive.sh b/browser_patches/chromium/archive.sh
index 8d81f611db..7297c8b60e 100755
--- a/browser_patches/chromium/archive.sh
+++ b/browser_patches/chromium/archive.sh
@@ -2,33 +2,170 @@
 set -e
 set +x
 
-if [[ ("$1" == "-h") || ("$1" == "--help") ]]; then
-  echo "usage: $(basename $0) [output-absolute-path]"
-  echo
-  echo "Generate distributable .zip archive from ./output folder that was previously downloaded."
-  echo
-  exit 0
-fi
-
-ZIP_PATH=$1
-if [[ $ZIP_PATH != /* ]]; then
-  echo "ERROR: path $ZIP_PATH is not absolute"
-  exit 1
-fi
-if [[ $ZIP_PATH != *.zip ]]; then
-  echo "ERROR: path $ZIP_PATH must have .zip extension"
-  exit 1
-fi
-if [[ -f $ZIP_PATH ]]; then
-  echo "ERROR: path $ZIP_PATH exists; can't do anything."
-  exit 1
-fi
-if ! [[ -d $(dirname $ZIP_PATH) ]]; then
-  echo "ERROR: folder for path $($ZIP_PATH) does not exist."
-  exit 1
-fi
-
 trap "cd $(pwd -P)" EXIT
 cd "$(dirname $0)"
+SCRIPT_PATH=$(pwd -P)
 
-cp output/build.zip $ZIP_PATH
+main() {
+  if [[ ("$1" == "-h") || ("$1" == "--help") ]]; then
+    echo "usage: $(basename $0) [output-absolute-path]"
+    echo
+    echo "Generate distributable .zip archive from ./output folder that was previously downloaded."
+    echo
+    exit 0
+  fi
+
+  ZIP_PATH=$1
+
+  if [[ $ZIP_PATH != /* ]]; then
+    echo "ERROR: path $ZIP_PATH is not absolute"
+    exit 1
+  fi
+  if [[ $ZIP_PATH != *.zip ]]; then
+    echo "ERROR: path $ZIP_PATH must have .zip extension"
+    exit 1
+  fi
+  if [[ -f $ZIP_PATH ]]; then
+    echo "ERROR: path $ZIP_PATH exists; can't do anything."
+    exit 1
+  fi
+  if ! [[ -d $(dirname $ZIP_PATH) ]]; then
+    echo "ERROR: folder for path $($ZIP_PATH) does not exist."
+    exit 1
+  fi
+
+  BUILD_TYPE=$2
+  if [[ "${BUILD_TYPE}" == "--compile"* ]]; then
+    archive_compiled_chromium "${BUILD_TYPE}"
+  elif [[ "${BUILD_TYPE}" == "--mirror"* ]]; then
+    archive_mirrored_chromium "${BUILD_TYPE}"
+  else
+    echo "ERROR: unknown build type - ${BUILD_TYPE}"
+    exit 1
+  fi
+
+  cd "${SCRIPT_PATH}"
+  cp output/build.zip $ZIP_PATH
+}
+
+function archive_compiled_chromium() {
+  CHROMIUM_FOLDER_NAME=""
+  CHROMIUM_FILES_TO_ARCHIVE=()
+
+  if [[ $1 == "--compile-mac"* ]]; then
+    CHROMIUM_FOLDER_NAME="chrome-mac"
+    CHROMIUM_FILES_TO_ARCHIVE=("Chromium.app")
+  elif [[ $1 == "--compile-linux" ]]; then
+    CHROMIUM_FOLDER_NAME="chrome-linux"
+    CHROMIUM_FILES_TO_ARCHIVE=(
+      "chrome"
+      "chrome_100_percent.pak"
+      "chrome_200_percent.pak"
+      "chrome_sandbox"
+      "chrome-wrapper"
+      "ClearKeyCdm"
+      "crashpad_handler"
+      "icudtl.dat"
+      "libEGL.so"
+      "libGLESv2.so"
+      "locales"
+      "MEIPreload"
+      "nacl_helper"
+      "nacl_helper_bootstrap"
+      "nacl_helper_nonsfi"
+      "nacl_irt_x86_64.nexe"
+      "product_logo_48.png"
+      "resources"
+      "resources.pak"
+      "swiftshader"
+      "v8_context_snapshot.bin"
+      "xdg-mime"
+      "xdg-settings"
+    )
+  elif [[ $1 == "--compile-win"* ]]; then
+    CHROMIUM_FOLDER_NAME="chrome-win"
+    CHROMIUM_FILES_TO_ARCHIVE=(
+      "chrome.dll"
+      "chrome.exe"
+      "chrome_100_percent.pak"
+      "chrome_200_percent.pak"
+      "chrome_elf.dll"
+      "chrome_proxy.exe"
+      "chrome_pwa_launcher.exe"
+      "D3DCompiler_47.dll"
+      "elevation_service.exe"
+      "eventlog_provider.dll"
+      "First Run"
+      "icudtl.dat"
+      "libEGL.dll"
+      "libGLESv2.dll"
+      "locales"
+      "MEIPreload"
+      "mojo_core.dll"
+      "nacl_irt_x86_64.nexe"
+      "notification_helper.exe"
+      "resources.pak"
+      "swiftshader/libEGL.dll"
+      "swiftshader/libGLESv2.dll"
+      "v8_context_snapshot.bin"
+    )
+  else
+    echo "ERROR: unknown command, use --help for details"
+    exit 1
+  fi
+
+  # Prepare resulting archive.
+  cd "$SCRIPT_PATH"
+  rm -rf output
+  mkdir -p "output/${CHROMIUM_FOLDER_NAME}"
+
+  # On Mac, use 'ditto' to copy directories instead of 'cp'.
+  COPY_COMMAND="cp -R"
+  if [[ $(uname) == "Darwin" ]]; then
+    COPY_COMMAND="ditto"
+  fi
+
+  for ((i = 0; i < ${#CHROMIUM_FILES_TO_ARCHIVE[@]}; i++)) do
+    file="${CHROMIUM_FILES_TO_ARCHIVE[$i]}"
+    mkdir -p "output/${CHROMIUM_FOLDER_NAME}/$(dirname $file)"
+    $COPY_COMMAND "${CR_CHECKOUT_PATH}/src/out/Default/${file}" "output/${CHROMIUM_FOLDER_NAME}/${file}"
+  done
+
+  if [[ $1 == "--compile-win"* ]]; then
+    $COPY_COMMAND "${CR_CHECKOUT_PATH}/src/out/Default/"*.manifest "output/${CHROMIUM_FOLDER_NAME}/"
+  fi
+
+  cd output
+  zip --symlinks -r build.zip "${CHROMIUM_FOLDER_NAME}"
+}
+
+archive_mirrored_chromium() {
+  cd "${SCRIPT_PATH}/output"
+
+  CHROMIUM_FOLDER_NAME=""
+  CHROMIUM_FILES_TO_REMOVE=()
+
+  PLATFORM="$1"
+  if [[ "${PLATFORM}" == "--mirror-win32" ]]; then
+    CHROMIUM_FOLDER_NAME="chrome-win"
+    CHROMIUM_FILES_TO_REMOVE+=("chrome-win/interactive_ui_tests.exe")
+  elif [[ "${PLATFORM}" == "--mirror-win64" ]]; then
+    CHROMIUM_FOLDER_NAME="chrome-win"
+    CHROMIUM_FILES_TO_REMOVE+=("chrome-win/interactive_ui_tests.exe")
+  elif [[ "${PLATFORM}" == "--mirror-mac" ]]; then
+    CHROMIUM_FOLDER_NAME="chrome-mac"
+  elif [[ "${PLATFORM}" == "--mirror-linux" ]]; then
+    CHROMIUM_FOLDER_NAME="chrome-linux"
+  else
+    echo "ERROR: unknown platform to build: $PLATFORM"
+    exit 1
+  fi
+
+  for file in ${CHROMIUM_FILES_TO_REMOVE[@]}; do
+    rm -f "${file}"
+  done
+
+  zip --symlinks -r build.zip "${CHROMIUM_FOLDER_NAME}"
+}
+
+main "$@"
diff --git a/browser_patches/chromium/build.sh b/browser_patches/chromium/build.sh
index bde1d06481..2d6bd030b4 100755
--- a/browser_patches/chromium/build.sh
+++ b/browser_patches/chromium/build.sh
@@ -36,6 +36,11 @@ compile_chromium() {
     exit 1
   fi
 
+  if [[ -z "${CR_CHECKOUT_PATH}/src" ]]; then
+    echo "ERROR: CR_CHECKOUT_PATH does not have src/ subfolder; is this a chromium checkout?"
+    exit 1
+  fi
+
   # install depot_tools if they are not in system
   # NOTE: as of Feb 8, 2021, windows requires manual and separate
   # installation of depot_tools.
@@ -46,114 +51,23 @@ compile_chromium() {
     export PATH="${SCRIPT_PATH}/depot_tools:$PATH"
   fi
 
-  CHROMIUM_FOLDER_NAME=""
-  CHROMIUM_FILES_TO_ARCHIVE=()
-
-  if [[ $1 == "--compile-mac-arm64" ]]; then
+  if [[ $1 == "--compile-mac"* ]]; then
     # As of Jan, 2021 Chromium mac compilation requires Xcode12.2
     if [[ ! -d /Applications/Xcode12.2.app ]]; then
-      echo "ERROR: chromium mac arm64 compilation requires XCode 12.2 to be available"
-      echo "in the Applications folder!"
+      echo "ERROR: chromium mac compilation requires /Applications/Xcode12.2.app"
+      echo "Download one from https://developer.apple.com/download/more/"
       exit 1
     fi
     export DEVELOPER_DIR=/Applications/Xcode12.2.app/Contents/Developer
     # As of Jan, 2021 Chromium mac compilation is only possible on Intel macbooks.
     # See https://chromium.googlesource.com/chromium/src.git/+/master/docs/mac_arm64.md
-    if [[ $(uname -m) != "x86_64" ]]; then
+    if [[ $1 == "--compile-mac-arm64" && $(uname -m) != "x86_64" ]]; then
       echo "ERROR: chromium mac arm64 compilation is (ironically) only supported on Intel Macbooks"
       exit 1
     fi
-    CHROMIUM_FOLDER_NAME="chrome-mac"
-    CHROMIUM_FILES_TO_ARCHIVE=("Chromium.app")
-  elif [[ $1 == "--compile-mac" ]]; then
-    export DEVELOPER_DIR=/Applications/Xcode12.2.app/Contents/Developer
-    CHROMIUM_FOLDER_NAME="chrome-mac"
-    CHROMIUM_FILES_TO_ARCHIVE=("Chromium.app")
-  elif [[ $1 == "--compile-linux" ]]; then
-    CHROMIUM_FOLDER_NAME="chrome-linux"
-    CHROMIUM_FILES_TO_ARCHIVE=(
-      "chrome"
-      "chrome_100_percent.pak"
-      "chrome_200_percent.pak"
-      "chrome_sandbox"
-      "chrome-wrapper"
-      "ClearKeyCdm"
-      "crashpad_handler"
-      "icudtl.dat"
-      "libEGL.so"
-      "libGLESv2.so"
-      "locales"
-      "MEIPreload"
-      "nacl_helper"
-      "nacl_helper_bootstrap"
-      "nacl_helper_nonsfi"
-      "nacl_irt_x86_64.nexe"
-      "product_logo_48.png"
-      "resources"
-      "resources.pak"
-      "swiftshader"
-      "v8_context_snapshot.bin"
-      "xdg-mime"
-      "xdg-settings"
-    )
-  elif [[ $1 == "--compile-win"* ]]; then
-    CHROMIUM_FOLDER_NAME="chrome-win"
-    CHROMIUM_FILES_TO_ARCHIVE=(
-      "chrome.dll"
-      "chrome.exe"
-      "chrome_100_percent.pak"
-      "chrome_200_percent.pak"
-      "chrome_elf.dll"
-      "chrome_proxy.exe"
-      "chrome_pwa_launcher.exe"
-      "D3DCompiler_47.dll"
-      "elevation_service.exe"
-      "eventlog_provider.dll"
-      "First Run"
-      "icudtl.dat"
-      "libEGL.dll"
-      "libGLESv2.dll"
-      "locales"
-      "MEIPreload"
-      "mojo_core.dll"
-      "nacl_irt_x86_64.nexe"
-      "notification_helper.exe"
-      "resources.pak"
-      "swiftshader/libEGL.dll"
-      "swiftshader/libGLESv2.dll"
-      "v8_context_snapshot.bin"
-    )
-  else
-    echo "ERROR: unknown command, use --help for details"
-    exit 1
   fi
 
-  # Get chromium SHA from the build revision.
-  # This will get us the last redirect URL from the crrev.com service.
-  REVISION_URL=$(curl -ILs -o /dev/null -w %{url_effective} "https://crrev.com/${CRREV}")
-  CRSHA="${REVISION_URL##*/}"
-
-  # Update Chromium checkout. One might think that this step should go to `prepare_checkout.sh`
-  # script, but the `prepare_checkout.sh` is in fact designed to prepare a fork checkout, whereas
-  # we don't fork Chromium.
-  #
-  # This is based on https://chromium.googlesource.com/chromium/src/+/master/docs/linux/build_instructions.md#get-the-code
-  if [[ ! -d "${CR_CHECKOUT_PATH}/src" ]]; then
-    rm -rf "${CR_CHECKOUT_PATH}"
-    mkdir -p "${CR_CHECKOUT_PATH}"
-    cd "${CR_CHECKOUT_PATH}"
-    fetch --nohooks chromium
-    cd src
-    if [[ $(uname) == "Linux" ]]; then
-      ./build/install-build-deps.sh
-    fi
-    gclient runhooks
-  fi
   cd "${CR_CHECKOUT_PATH}/src"
-  git checkout master
-  git pull origin master
-  git checkout "${CRSHA}"
-  gclient sync
 
   # Prepare build folder.
   mkdir -p "./out/Default"
@@ -196,30 +110,6 @@ EOF
       ninja -j 200 -C out/Default $TARGETS
     fi
   fi
-
-  # Prepare resulting archive.
-  cd "$SCRIPT_PATH"
-  rm -rf output
-  mkdir -p "output/${CHROMIUM_FOLDER_NAME}"
-
-  # On Mac, use 'ditto' to copy directories instead of 'cp'.
-  COPY_COMMAND="cp -R"
-  if [[ $(uname) == "Darwin" ]]; then
-    COPY_COMMAND="ditto"
-  fi
-
-  for ((i = 0; i < ${#CHROMIUM_FILES_TO_ARCHIVE[@]}; i++)) do
-    file="${CHROMIUM_FILES_TO_ARCHIVE[$i]}"
-    mkdir -p "output/${CHROMIUM_FOLDER_NAME}/$(dirname $file)"
-    $COPY_COMMAND "${CR_CHECKOUT_PATH}/src/out/Default/${file}" "output/${CHROMIUM_FOLDER_NAME}/${file}"
-  done
-
-  if [[ $1 == "--compile-win"* ]]; then
-    $COPY_COMMAND "${CR_CHECKOUT_PATH}/src/out/Default/"*.manifest "output/${CHROMIUM_FOLDER_NAME}/"
-  fi
-
-  cd output
-  zip --symlinks -r build.zip "${CHROMIUM_FOLDER_NAME}"
 }
 
 mirror_chromium() {
@@ -229,8 +119,6 @@ mirror_chromium() {
   cd output
 
   CHROMIUM_URL=""
-  CHROMIUM_FOLDER_NAME=""
-  CHROMIUM_FILES_TO_REMOVE=()
 
   PLATFORM="$1"
   if [[ "${PLATFORM}" == "--mirror" ]]; then
@@ -249,18 +137,12 @@ mirror_chromium() {
 
   if [[ "${PLATFORM}" == "--mirror-win32" ]]; then
     CHROMIUM_URL="https://storage.googleapis.com/chromium-browser-snapshots/Win/${CRREV}/chrome-win.zip"
-    CHROMIUM_FOLDER_NAME="chrome-win"
-    CHROMIUM_FILES_TO_REMOVE+=("chrome-win/interactive_ui_tests.exe")
   elif [[ "${PLATFORM}" == "--mirror-win64" ]]; then
     CHROMIUM_URL="https://storage.googleapis.com/chromium-browser-snapshots/Win_x64/${CRREV}/chrome-win.zip"
-    CHROMIUM_FOLDER_NAME="chrome-win"
-    CHROMIUM_FILES_TO_REMOVE+=("chrome-win/interactive_ui_tests.exe")
   elif [[ "${PLATFORM}" == "--mirror-mac" ]]; then
     CHROMIUM_URL="https://storage.googleapis.com/chromium-browser-snapshots/Mac/${CRREV}/chrome-mac.zip"
-    CHROMIUM_FOLDER_NAME="chrome-mac"
   elif [[ "${PLATFORM}" == "--mirror-linux" ]]; then
     CHROMIUM_URL="https://storage.googleapis.com/chromium-browser-snapshots/Linux_x64/${CRREV}/chrome-linux.zip"
-    CHROMIUM_FOLDER_NAME="chrome-linux"
   else
     echo "ERROR: unknown platform to build: $1"
     exit 1
@@ -270,11 +152,6 @@ mirror_chromium() {
 
   curl --output chromium-upstream.zip "${CHROMIUM_URL}"
   unzip chromium-upstream.zip
-  for file in ${CHROMIUM_FILES_TO_REMOVE[@]}; do
-    rm -f "${file}"
-  done
-
-  zip --symlinks -r build.zip "${CHROMIUM_FOLDER_NAME}"
 }
 
 main $1
diff --git a/browser_patches/prepare_checkout.sh b/browser_patches/prepare_checkout.sh
index 83293a095d..1f3d2a634a 100755
--- a/browser_patches/prepare_checkout.sh
+++ b/browser_patches/prepare_checkout.sh
@@ -4,6 +4,7 @@ set +x
 
 trap "cd $(pwd -P)" EXIT
 cd "$(dirname "$0")"
+SCRIPT_PATH=$(pwd -P)
 
 REMOTE_BROWSER_UPSTREAM="browser_upstream"
 BUILD_BRANCH="playwright-build"
@@ -26,6 +27,41 @@ if [[ $# == 0 ]]; then
   exit 1
 fi
 
+function prepare_chromium_checkout {
+  cd "${SCRIPT_PATH}"
+  if [[ -z "${CR_CHECKOUT_PATH}" ]]; then
+    echo "ERROR: chromium compilation requires CR_CHECKOUT_PATH to be set to reuse checkout."
+    echo "NOTE: we expect '\$CR_CHECKOUT_PATH/src' to exist to be a valid chromium checkout."
+    exit 1
+  fi
+
+  # Get chromium SHA from the build revision.
+  # This will get us the last redirect URL from the crrev.com service.
+  CRREV=$(head -1 ./chromium/BUILD_NUMBER)
+  REVISION_URL=$(curl -ILs -o /dev/null -w %{url_effective} "https://crrev.com/${CRREV}")
+  CRSHA="${REVISION_URL##*/}"
+
+  # Update Chromium checkout.
+  #
+  # This is based on https://chromium.googlesource.com/chromium/src/+/master/docs/linux/build_instructions.md#get-the-code
+  if [[ ! -d "${CR_CHECKOUT_PATH}/src" ]]; then
+    rm -rf "${CR_CHECKOUT_PATH}"
+    mkdir -p "${CR_CHECKOUT_PATH}"
+    cd "${CR_CHECKOUT_PATH}"
+    fetch --nohooks chromium
+    cd src
+    if [[ $(uname) == "Linux" ]]; then
+      ./build/install-build-deps.sh
+    fi
+    gclient runhooks
+  fi
+  cd "${CR_CHECKOUT_PATH}/src"
+  git checkout master
+  git pull origin master
+  git checkout "${CRSHA}"
+  gclient sync -D
+}
+
 # FRIENDLY_CHECKOUT_PATH is used only for logging.
 FRIENDLY_CHECKOUT_PATH="";
 CHECKOUT_PATH=""
@@ -34,7 +70,7 @@ BUILD_NUMBER=""
 WEBKIT_EXTRA_FOLDER_PATH=""
 FIREFOX_EXTRA_FOLDER_PATH=""
 if [[ ("$1" == "chromium") || ("$1" == "chromium/") || ("$1" == "cr") ]]; then
-  echo "FYI: chromium checkout is not supported. Use '//browser_patches/chromium/build.sh' instead"
+  prepare_chromium_checkout
   exit 0
 elif [[ ("$1" == "ffmpeg") || ("$1" == "ffmpeg/") ]]; then
   echo "FYI: ffmpeg checkout is not supported. Use '//browser_patches/ffmpeg/build.sh' instead"