Adding upstream version 115.7.0esr.upstream/115.7.0esr

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

29 files changed, 2962 insertions, 0 deletions

diff --git a/dom/media/webrtc/third_party_build/README.md b/dom/media/webrtc/third_party_build/README.md
new file mode 100644
index 0000000000..9151445c87
--- /dev/null
+++ b/dom/media/webrtc/third_party_build/README.md
@@ -0,0 +1,17 @@
+# Vendoring libwebrtc and the fast-forward process
+
+Most of the important information about this process is contained on the fast-forward
+automation wiki page
+[here](https://wiki.mozilla.org/Media/WebRTC/libwebrtc_Update_Process/automation_plan).
+
+To skip the history and details and go directly to starting the libwebrtc fast-foward
+process, go to the
+[Operation Checklist](https://wiki.mozilla.org/Media/WebRTC/libwebrtc_Update_Process/automation_plan#Operation_Checklist).
+
+# Fixing errors reported in scripts
+
+In most cases, the scripts report errors including suggestions on how to resolve the
+issue.  If you're seeing an error message referring you to this README.md file, the
+likely issue is that you're missing environment variables that should be set in a
+config_env file in .moz-fast-forward.  The default for that file can be found at
+dom/media/webrtc/third_party_build/default_config_env.
diff --git a/dom/media/webrtc/third_party_build/build_no_op_commits.sh b/dom/media/webrtc/third_party_build/build_no_op_commits.sh
new file mode 100644
index 0000000000..eff61a5eb5
--- /dev/null
+++ b/dom/media/webrtc/third_party_build/build_no_op_commits.sh
@@ -0,0 +1,126 @@
+#!/bin/bash
+
+function show_error_msg()
+{
+  echo "*** ERROR *** $? line $1 $0 did not complete successfully!"
+  echo "$ERROR_HELP"
+}
+ERROR_HELP=""
+
+# Print an Error message if `set -eE` causes the script to exit due to a failed command
+trap 'show_error_msg $LINENO' ERR
+
+source dom/media/webrtc/third_party_build/use_config_env.sh
+
+echo "MOZ_LIBWEBRTC_SRC: $MOZ_LIBWEBRTC_SRC"
+
+# After this point:
+# * eE: All commands should succeed.
+# * u: All variables should be defined before use.
+# * o pipefail: All stages of all pipes should succeed.
+set -eEuo pipefail
+
+CURRENT_DIR=`pwd`
+cd $MOZ_LIBWEBRTC_SRC
+
+MANUAL_INTERVENTION_COMMIT_FILE="$TMP_DIR/manual_commits.txt"
+rm -f $MANUAL_INTERVENTION_COMMIT_FILE
+
+# Find the common commit between our previous work branch and trunk
+CURRENT_RELEASE_BASE=`git merge-base branch-heads/$MOZ_PRIOR_UPSTREAM_BRANCH_HEAD_NUM master`
+
+# Write no-op files for the cherry-picked release branch commits.  For more
+# details on what this is doing, see make_upstream_revert_noop.sh.
+COMMITS=`git log -r $CURRENT_RELEASE_BASE..branch-heads/$MOZ_PRIOR_UPSTREAM_BRANCH_HEAD_NUM --format='%h'`
+for commit in $COMMITS; do
+
+  echo "Processing release branch commit $commit for no-op handling"
+
+  # Don't process the commit if the commit message is missing the customary
+  # line that shows which upstream commit is being cherry-picked.
+  CNT=`git show $commit | grep "cherry picked from commit" | wc -l | tr -d " " || true`
+  if [ $CNT != 1 ]; then
+    # record the commit to list at the end of this script as
+    # 'needing intervention'
+    echo "    no cherry-pick info found, skipping commit $commit"
+    echo "$commit" >> $MANUAL_INTERVENTION_COMMIT_FILE
+    continue
+  fi
+
+  CHERRY_PICK_COMMIT=`git show $commit | grep "cherry picked from commit" | tr -d "()" | awk '{ print $5; }'`
+  SHORT_SHA=`git show --name-only $CHERRY_PICK_COMMIT --format='%h' | head -1`
+  echo "    commit $commit cherry-picks $SHORT_SHA"
+
+  echo "We already cherry-picked this when we vendored $commit." \
+  > $STATE_DIR/$SHORT_SHA.no-op-cherry-pick-msg
+
+done
+
+# This section checks for commits that may have been cherry-picked in more
+# than one release branch.
+TARGET_RELEASE_BASE=`git merge-base $MOZ_TARGET_UPSTREAM_BRANCH_HEAD master`
+NEW_COMMITS=`git log -r $TARGET_RELEASE_BASE..$MOZ_TARGET_UPSTREAM_BRANCH_HEAD --format='%h'`
+
+# Convert the files that we've already generated for no-op detection into
+# something that we can use as a regular expression for searching.
+KNOWN_NO_OP_COMMITS=`cd $STATE_DIR ; \
+  ls *.no-op-cherry-pick-msg \
+  | sed 's/\.no-op-cherry-pick-msg//' \
+  | paste -sd '|' /dev/stdin`
+
+for commit in $NEW_COMMITS; do
+
+  echo "Processing next release branch commit $commit for no-op handling"
+
+  # Don't process the commit if the commit message is missing the customary
+  # line that shows which upstream commit is being cherry-picked.
+  CNT=`git show $commit | grep "cherry picked from commit" | wc -l | tr -d " " || true`
+  if [ $CNT != 1 ]; then
+    # record the commit to list at the end of this script as
+    # 'needing intervention'
+    echo "    no cherry-pick info found, skipping commit $commit"
+    echo "$commit" >> $MANUAL_INTERVENTION_COMMIT_FILE
+    continue
+  fi
+
+  CHERRY_PICK_COMMIT=`git show $commit | grep "cherry picked from commit" | tr -d "()" | awk '{ print $5; }'`
+  SHORT_SHA=`git show --name-only $CHERRY_PICK_COMMIT --format='%h' | head -1`
+
+  # The trick here is that we only want to include no-op processing for the
+  # commits that appear both here _and_ in the previous release's cherry-pick
+  # commits.  We check the known list of no-op commits to see if it was
+  # cherry picked in the previous release branch and then create another
+  # file for the new release branch commit that will ultimately be a no-op.
+  if [[ "$SHORT_SHA" =~ ^($KNOWN_NO_OP_COMMITS)$ ]]; then
+    echo "    commit $commit cherry-picks $SHORT_SHA"
+    cp $STATE_DIR/$SHORT_SHA.no-op-cherry-pick-msg $STATE_DIR/$commit.no-op-cherry-pick-msg
+  fi
+
+done
+
+if [ ! -f $MANUAL_INTERVENTION_COMMIT_FILE ]; then
+  echo "No commits require manual intervention"
+  exit
+fi
+
+echo $"
+Each of the following commits requires manual intervention to
+verify the source of the cherry-pick or there may be errors
+reported during the fast-forward processing.  Without this
+intervention, the common symptom is that the vendored commit
+file count (0) will not match the upstream commit file count.
+"
+
+for commit in `cat $MANUAL_INTERVENTION_COMMIT_FILE`; do
+  SUMMARY=`git show --oneline --name-only $commit | head -1`
+  echo "  '$SUMMARY'"
+done
+
+echo $"
+To manually create the no-op tracking files needed,
+run the following command for each commit in question:
+  ( export UPSTREAM_COMMIT=\"{sha-of-upstream-commit}\" ; \\
+    export PICKED_COMMIT=\"{sha-of-already-used-commit}\" ; \\
+    echo \"We already cherry-picked this when we vendored \$PICKED_COMMIT.\" \\
+    > $STATE_DIR/\$UPSTREAM_COMMIT.no-op-cherry-pick-msg )
+"
diff --git a/dom/media/webrtc/third_party_build/commit-build-file-changes.sh b/dom/media/webrtc/third_party_build/commit-build-file-changes.sh
new file mode 100644
index 0000000000..2b4c791fca
--- /dev/null
+++ b/dom/media/webrtc/third_party_build/commit-build-file-changes.sh
@@ -0,0 +1,47 @@
+#!/bin/bash
+
+function show_error_msg()
+{
+  echo "*** ERROR *** $? line $1 $0 did not complete successfully!"
+  echo "$ERROR_HELP"
+}
+ERROR_HELP=""
+
+# Print an Error message if `set -eE` causes the script to exit due to a failed command
+trap 'show_error_msg $LINENO' ERR
+
+# All commands should be printed as they are executed
+# set -x
+
+# After this point:
+# * eE: All commands should succede.
+# * u: All variables should be defined before use.
+# * o pipefail: All stages of all pipes should succede.
+set -eEuo pipefail
+
+MOZ_BUILD_CHANGE_CNT=`hg status third_party/libwebrtc | wc -l | tr -d " "`
+echo "MOZ_BUILD_CHANGE_CNT: $MOZ_BUILD_CHANGE_CNT"
+if [ "x$MOZ_BUILD_CHANGE_CNT" != "x0" ]; then
+  CURRENT_COMMIT_SHA=`hg id -i | sed 's/+//'`
+  COMMIT_DESC=`hg --config alias.log=log log -T '{desc|firstline}' -r $CURRENT_COMMIT_SHA`
+
+  # since we have build file changes, touch the CLOBBER file
+  cat CLOBBER | egrep "^#|^$" > CLOBBER.new
+  mv CLOBBER.new CLOBBER
+  echo "Modified build files in third_party/libwebrtc - $COMMIT_DESC" >> CLOBBER
+
+  ADD_CNT=`hg status -nu third_party/libwebrtc | wc -l | tr -d " "`
+  DEL_CNT=`hg status -nd third_party/libwebrtc | wc -l | tr -d " "`
+  if [ "x$ADD_CNT" != "x0" ]; then
+    hg status -nu third_party/libwebrtc | xargs hg add
+  fi
+  if [ "x$DEL_CNT" != "x0" ]; then
+    hg status -nd third_party/libwebrtc | xargs hg rm
+  fi
+
+  hg commit -m \
+    "$COMMIT_DESC - moz.build file updates" \
+    third_party/libwebrtc CLOBBER
+fi
+
+echo "Done in $0"
diff --git a/dom/media/webrtc/third_party_build/default_config_env b/dom/media/webrtc/third_party_build/default_config_env
new file mode 100644
index 0000000000..a50694f0e3
--- /dev/null
+++ b/dom/media/webrtc/third_party_build/default_config_env
@@ -0,0 +1,42 @@
+#!/bin/bash
+
+# Edit {path-to} to match the location of your copy of Mozilla's
+# fork of libwebrtc (at https://github.com/mozilla/libwebrtc).
+export MOZ_LIBWEBRTC_SRC=$STATE_DIR/moz-libwebrtc
+
+# Fast-forwarding each Chromium version of libwebrtc should be done
+# under a separate bugzilla bug.  This bug number is used when crafting
+# the commit summary as each upstream commit is vendored into the
+# mercurial repository.  The bug used for the v106 fast-forward was
+# 1800920.
+export MOZ_FASTFORWARD_BUG="1833237"
+
+# MOZ_NEXT_LIBWEBRTC_MILESTONE and MOZ_NEXT_FIREFOX_REL_TARGET are
+# not used during fast-forward processing, but facilitate generating this
+# default config.  To generate an default config for the next update, run
+# bash dom/media/webrtc/third_party_build/update_default_config_env.sh
+export MOZ_NEXT_LIBWEBRTC_MILESTONE=112
+export MOZ_NEXT_FIREFOX_REL_TARGET=116
+
+# For Chromium release branches, see:
+# https://chromiumdash.appspot.com/branches
+
+# Chromium's v111 release branch was 5563.  This is used to pre-stack
+# the previous release branch's commits onto the appropriate base commit
+# (the first common commit between trunk and the release branch).
+export MOZ_PRIOR_UPSTREAM_BRANCH_HEAD_NUM="5563"
+
+# New target release branch for v112 is branch-heads/5615.  This is used
+# to calculate the next upstream commit.
+export MOZ_TARGET_UPSTREAM_BRANCH_HEAD="branch-heads/5615"
+
+# For local development 'mozpatches' is fine for a branch name, but when
+# pushing the patch stack to github, it should be named something like
+# 'moz-mods-chr112-for-rel116'.
+export MOZ_LIBWEBRTC_BRANCH="mozpatches"
+
+# After elm has been merged to mozilla-central, the patch stack in
+# moz-libwebrtc should be pushed to github.  The script
+# push_official_branch.sh uses this branch name when pushing to the
+# public repo.
+export MOZ_LIBWEBRTC_OFFICIAL_BRANCH="moz-mods-chr112-for-rel116"
diff --git a/dom/media/webrtc/third_party_build/detect_upstream_revert.sh b/dom/media/webrtc/third_party_build/detect_upstream_revert.sh
new file mode 100644
index 0000000000..2dc868952d
--- /dev/null
+++ b/dom/media/webrtc/third_party_build/detect_upstream_revert.sh
@@ -0,0 +1,93 @@
+#!/bin/bash
+
+function show_error_msg()
+{
+  echo "*** ERROR *** $? line $1 $0 did not complete successfully!"
+  echo "$ERROR_HELP"
+}
+ERROR_HELP=""
+
+# Print an Error message if `set -eE` causes the script to exit due to a failed command
+trap 'show_error_msg $LINENO' ERR
+
+source dom/media/webrtc/third_party_build/use_config_env.sh
+
+# If DEBUG_GEN is set all commands should be printed as they are executed
+if [ ! "x$DEBUG_GEN" = "x" ]; then
+  set -x
+fi
+
+if [ "x$MOZ_LIBWEBRTC_SRC" = "x" ]; then
+  echo "MOZ_LIBWEBRTC_SRC is not defined, see README.md"
+  exit
+fi
+
+if [ -d $MOZ_LIBWEBRTC_SRC ]; then
+  echo "MOZ_LIBWEBRTC_SRC is $MOZ_LIBWEBRTC_SRC"
+else
+  echo "Path $MOZ_LIBWEBRTC_SRC is not found, see README.md"
+  exit
+fi
+
+if [ "x$MOZ_LIBWEBRTC_BRANCH" = "x" ]; then
+  echo "MOZ_LIBWEBRTC_BRANCH is not defined, see README.md"
+  exit
+fi
+
+if [ "x$AUTO_FIX_REVERT_AS_NOOP" = "x" ]; then
+  AUTO_FIX_REVERT_AS_NOOP="0"
+fi
+
+find_base_commit
+find_next_commit
+
+MOZ_LIBWEBRTC_COMMIT_MSG=`cd $MOZ_LIBWEBRTC_SRC ; \
+git show --name-only --oneline $MOZ_LIBWEBRTC_NEXT_BASE \
+ | head -1 | sed 's/[^ ]* //'`
+
+echo "MOZ_LIBWEBRTC_BASE: $MOZ_LIBWEBRTC_BASE"
+echo "MOZ_LIBWEBRTC_NEXT_BASE: $MOZ_LIBWEBRTC_NEXT_BASE"
+echo "MOZ_LIBWEBRTC_COMMIT_MSG: $MOZ_LIBWEBRTC_COMMIT_MSG"
+export MOZ_LIBWEBRTC_REVERT_SHA=`cd $MOZ_LIBWEBRTC_SRC ; \
+git log --oneline -r $MOZ_LIBWEBRTC_BASE..$MOZ_TARGET_UPSTREAM_BRANCH_HEAD \
+ | grep -F "Revert \"$MOZ_LIBWEBRTC_COMMIT_MSG" \
+ | tail -1 | awk '{print $1;}' || true`
+
+echo "MOZ_LIBWEBRTC_REVERT_SHA: $MOZ_LIBWEBRTC_REVERT_SHA"
+
+if [ "x$MOZ_LIBWEBRTC_REVERT_SHA" == "x" ]; then
+  echo "no revert commit detected"
+  exit
+fi
+
+if [ "x$AUTO_FIX_REVERT_AS_NOOP" = "x1" ]; then
+  echo "AUTO_FIX_REVERT_AS_NOOP detected, fixing land/revert pair automatically"
+  bash $SCRIPT_DIR/make_upstream_revert_noop.sh
+  exit
+fi
+
+echo $"
+The next upstream commit has a corresponding future \"Revert\" commit.
+
+There are 2 common ways forward in this situation:
+1. If you're relatively certain there will not be rebase conflicts in the
+   github repo ($MOZ_LIBWEBRTC_SRC), simply run:
+       SKIP_NEXT_REVERT_CHK=1 bash $SCRIPT_DIR/loop-ff.sh
+
+2. The surer method for no rebase conflicts is to cherry-pick both the
+   next commit, and the commit that reverts the next commit onto the
+   bottom of our patch stack in github.  This pushes the likely rebase
+   conflict into the future when the upstream fix is relanded, but
+   ensures we only have to deal with the conflict once.  The following
+   commands will add the necessary commits to the bottom of our patch
+   stack in github, and leave indicator files in the home directory that
+   help loop-ff know when to invoke special no-op commit handling:
+
+       MOZ_LIBWEBRTC_BASE=$MOZ_LIBWEBRTC_BASE \\
+       MOZ_LIBWEBRTC_NEXT_BASE=$MOZ_LIBWEBRTC_NEXT_BASE \\
+       MOZ_LIBWEBRTC_REVERT_SHA=$MOZ_LIBWEBRTC_REVERT_SHA \\
+       bash $SCRIPT_DIR/make_upstream_revert_noop.sh
+
+       SKIP_NEXT_REVERT_CHK=1 bash $SCRIPT_DIR/loop-ff.sh
+"
+exit 1
diff --git a/dom/media/webrtc/third_party_build/elm_arcconfig.patch b/dom/media/webrtc/third_party_build/elm_arcconfig.patch
new file mode 100644
index 0000000000..46adb9c6f1
--- /dev/null
+++ b/dom/media/webrtc/third_party_build/elm_arcconfig.patch
@@ -0,0 +1,10 @@
+diff --git a/.arcconfig b/.arcconfig
+--- a/.arcconfig
++++ b/.arcconfig
+@@ -1,5 +1,5 @@
+ {
+   "phabricator.uri" : "https://phabricator.services.mozilla.com/",
+-  "repository.callsign": "MOZILLACENTRAL",
++  "repository.callsign": "ELM",
+   "history.immutable": false
+ }
diff --git a/dom/media/webrtc/third_party_build/elm_rebase.sh b/dom/media/webrtc/third_party_build/elm_rebase.sh
new file mode 100644
index 0000000000..4d53373d35
--- /dev/null
+++ b/dom/media/webrtc/third_party_build/elm_rebase.sh
@@ -0,0 +1,247 @@
+#!/bin/bash
+
+# This script exists to help with the rebase process on elm.  It rebases
+# each patch individually to make it easier to fix rebase conflicts
+# without jeopardizing earlier, sucessfully rebased commits. In order to
+# limit rebase conflicts around generated moz.build files, it regenerates
+# moz.build file commits.  It also ensures any commits with 'FLOAT' in the
+# commit summary are pushed to the top of the fast-forward stack to help
+# the sheriffs more easily merge our commit stack from elm to moz-central.
+#
+# Occasionally, there will be upstream vendored commits that break the
+# build file generation with follow on commits that fix that error. In
+# order to allow the rebase process to work more smoothly, it is possible
+# to annotate a commit with the string '(skip-generation)' and normal
+# build file generation (detected with changes to BUILD.gn files) is
+# disabled for that commit.  The script outputs instructions for handling
+# this situation.
+#
+# Note: the very first rebase operation will require some manual
+# intervention. The user will need to provide, at minimum, the commit that
+# corresponds to moz-central upon which the fast-forward stack is based.
+# It may also be necessary to provide the first commit of the
+# fast-forward stack.  Example:
+#   MOZ_BOTTOM_FF=30f0afb7e4c5 \
+#   MOZ_CURRENT_CENTRAL=cad1bd47c273 \
+#   bash dom/media/webrtc/third_party_build/elm_rebase.sh
+#
+# Assumes the top of the fast-forward stack to rebase is the current revision,
+# ".".
+
+function show_error_msg()
+{
+  echo "*** ERROR *** $? line $1 $0 did not complete successfully!"
+  echo "$ERROR_HELP"
+}
+ERROR_HELP=""
+
+# Print an Error message if `set -eE` causes the script to exit due to a failed command
+trap 'show_error_msg $LINENO' ERR
+
+source dom/media/webrtc/third_party_build/use_config_env.sh
+
+GENERATION_ERROR=$"
+Generating build files has failed.  The most common reason for this
+failure is that the current commit has an upcoming '(fix-xxxxxx)' commit
+that will then allow the build file generation to complete.  If the
+current situation seems to fit that pattern, adding a line with
+'(skip-generation)' to the commit message will ensure that future rebase
+operations do not attempt to generate build files for this commit.  It may
+be as simple as running the following commands:
+  HGPLAIN=1 hg log -T '{desc}' -r tip > $TMP_DIR/commit_message.txt
+  ed -s $TMP_DIR/commit_message.txt <<< $'3i\n(skip-generation)\n\n.\nw\nq'
+  hg commit --amend -l $TMP_DIR/commit_message.txt
+  bash $0
+"
+COMMIT_LIST_FILE=$TMP_DIR/rebase-commit-list.txt
+export HGPLAIN=1
+
+# After this point:
+# * eE: All commands should succeed.
+# * o pipefail: All stages of all pipes should succeed.
+set -eEo pipefail
+
+if [ -f $STATE_DIR/rebase_resume_state ]; then
+  source $STATE_DIR/rebase_resume_state
+else
+
+  if [ "x" == "x$MOZ_TOP_FF" ]; then
+    MOZ_TOP_FF=`hg log -r . -T"{node|short}"`
+
+    ERROR_HELP=$"
+The topmost commit to be rebased is not in the public phase. Should it be
+pushed to elm first? If this is intentional, please rerun the command and pass
+it in explicitly:
+  MOZ_TOP_FF=$MOZ_TOP_FF bash $0
+"
+    if [[ $(hg phase -r .) != *public ]]; then
+      echo "$ERROR_HELP"
+      exit 1
+    fi
+    ERROR_HELP=""
+
+    ERROR_HELP=$"
+The topmost commit to be rebased is public but has descendants. If those
+descendants should not be rebased, please rerun the command and pass the commit
+in explicitly:
+  MOZ_TOP_FF=$MOZ_TOP_FF bash $0
+"
+    if [ "x" != "x$(hg log -r 'descendants(.) and !.' -T'{node|short}')" ]; then
+      echo "$ERROR_HELP"
+      exit 1
+    fi
+    ERROR_HELP=""
+  fi
+
+  ERROR_HELP=$"
+An error here is likely because no revision for central is found.
+One possible reason for this is this is your first rebase operation.
+To 'bootstrap' the first rebase operation, please find the
+moz-central commit that the vendoring commits is based on, and
+rerun the command:
+  MOZ_CURRENT_CENTRAL={central-sha} bash $0
+
+You may also need to provide the bottom commit of the fast-forward
+stack.  The bottom commit means the commit following central.  This
+could be the sha of the .arcconfig commit if it is the bottom commit.
+That command looks like:
+  MOZ_BOTTOM_FF={base-sha} MOZ_CURRENT_CENTRAL={central-sha} bash $0
+"
+  if [ "x" == "x$MOZ_CURRENT_CENTRAL" ]; then
+    MOZ_CURRENT_CENTRAL=`hg log -r central -T"{node|short}"`
+  fi
+  if [ "x" == "x$MOZ_BOTTOM_FF" ]; then
+    MOZ_BOTTOM_FF=`hg log -r $MOZ_CURRENT_CENTRAL~-1 -T"{node|short}"`
+  fi
+  ERROR_HELP=""
+
+  if [ "x" == "x$MOZ_BOTTOM_FF" ]; then
+    echo "No value found for the bottom commit of the fast-forward commit stack."
+    exit 1
+  fi
+
+  # After this point:
+  # * eE: All commands should succeed.
+  # * u: All variables should be defined before use.
+  # * o pipefail: All stages of all pipes should succeed.
+  set -eEuo pipefail
+
+  hg pull central
+  MOZ_NEW_CENTRAL=`hg log -r central -T"{node|short}"`
+
+  echo "moz-central in elm is currently $MOZ_CURRENT_CENTRAL"
+  echo "bottom of fast-foward tree is $MOZ_BOTTOM_FF"
+  echo "top of fast-forward tree (webrtc-fast-forward) is $MOZ_TOP_FF"
+  echo "new target for elm rebase $MOZ_NEW_CENTRAL (tip of moz-central)"
+
+  hg log -T '{rev}:{node|short} {desc|firstline}\n' \
+      -r $MOZ_BOTTOM_FF::$MOZ_TOP_FF > $COMMIT_LIST_FILE
+
+  # move all FLOAT lines to end of file, and delete the "empty" tilde line
+  # line at the beginning
+  ed -s $COMMIT_LIST_FILE <<< $'g/- FLOAT -/m$\ng/^~$/d\nw\nq'
+
+  MOZ_BOOKMARK=`date "+webrtc-fast-forward-%Y-%m-%d--%H-%M"`
+  hg bookmark -r elm $MOZ_BOOKMARK
+
+  hg update $MOZ_NEW_CENTRAL
+
+  # pre-work is complete, let's write out a temporary config file that allows
+  # us to resume
+  echo $"export MOZ_CURRENT_CENTRAL=$MOZ_CURRENT_CENTRAL
+export MOZ_BOTTOM_FF=$MOZ_BOTTOM_FF
+export MOZ_TOP_FF=$MOZ_TOP_FF
+export MOZ_NEW_CENTRAL=$MOZ_NEW_CENTRAL
+export MOZ_BOOKMARK=$MOZ_BOOKMARK
+" > $STATE_DIR/rebase_resume_state
+fi # if [ -f $STATE_DIR/rebase_resume_state ]; then ; else
+
+# grab all commits
+COMMITS=`cat $COMMIT_LIST_FILE | awk '{print $1;}'`
+
+echo -n "Commits: "
+for commit in $COMMITS; do
+echo -n "$commit "
+done
+echo ""
+
+for commit in $COMMITS; do
+  echo "Processing $commit"
+  FULL_COMMIT_LINE=`head -1 $COMMIT_LIST_FILE`
+
+  function remove_commit () {
+    echo "Removing from list '$FULL_COMMIT_LINE'"
+    ed -s $COMMIT_LIST_FILE <<< $'1d\nw\nq'
+  }
+
+  IS_BUILD_COMMIT=`hg log -T '{desc|firstline}' -r $commit \
+                   | grep "file updates" | wc -l | tr -d " " || true`
+  echo "IS_BUILD_COMMIT: $IS_BUILD_COMMIT"
+  if [ "x$IS_BUILD_COMMIT" != "x0" ]; then
+    echo "Skipping $commit:"
+    hg log -T '{desc|firstline}' -r $commit
+    remove_commit
+    continue
+  fi
+
+  IS_SKIP_GEN_COMMIT=`hg log --verbose \
+                         -r $commit \
+                      | grep "skip-generation" | wc -l | tr -d " " || true`
+  echo "IS_SKIP_GEN_COMMIT: $IS_SKIP_GEN_COMMIT"
+
+  echo "Generate patch for: $commit"
+  hg export -r $commit > $TMP_DIR/rebase.patch
+
+  echo "Import patch for $commit"
+  hg import $TMP_DIR/rebase.patch || \
+  ( hg log -T '{desc}' -r $commit > $TMP_DIR/rebase_commit_message.txt ; \
+    remove_commit ; \
+    echo "Error importing: '$FULL_COMMIT_LINE'" ; \
+    echo "Please fix import errors, then:" ; \
+    echo "  hg commit -l $TMP_DIR/rebase_commit_message.txt" ; \
+    echo "  bash $0" ; \
+    exit 1 )
+
+  remove_commit
+
+  if [ "x$IS_SKIP_GEN_COMMIT" != "x0" ]; then
+    echo "Skipping build generation for $commit"
+    continue
+  fi
+
+  MODIFIED_BUILD_RELATED_FILE_CNT=`hg diff -c tip --stat \
+      --include 'third_party/libwebrtc/**BUILD.gn' \
+      --include 'third_party/libwebrtc/webrtc.gni' \
+      --include 'dom/media/webrtc/third_party_build/gn-configs/webrtc.json' \
+      | wc -l | tr -d " "`
+  echo "MODIFIED_BUILD_RELATED_FILE_CNT: $MODIFIED_BUILD_RELATED_FILE_CNT"
+  if [ "x$MODIFIED_BUILD_RELATED_FILE_CNT" != "x0" ]; then
+    echo "Regenerate build files"
+    ./mach python python/mozbuild/mozbuild/gn_processor.py \
+        dom/media/webrtc/third_party_build/gn-configs/webrtc.json || \
+    ( echo "$GENERATION_ERROR" ; exit 1 )
+
+    MOZ_BUILD_CHANGE_CNT=`hg status third_party/libwebrtc \
+        --include 'third_party/libwebrtc/**moz.build' | wc -l | tr -d " "`
+    if [ "x$MOZ_BUILD_CHANGE_CNT" != "x0" ]; then
+      bash dom/media/webrtc/third_party_build/commit-build-file-changes.sh
+      NEWEST_COMMIT=`hg log -T '{desc|firstline}' -r tip`
+      echo "NEWEST_COMMIT: $NEWEST_COMMIT"
+      echo "NEWEST_COMMIT: $NEWEST_COMMIT" >> $LOG_DIR/rebase-build-changes-commits.log
+    fi
+    echo "Done generating build files"
+  fi
+
+  echo "Done processing $commit"
+done
+
+rm $STATE_DIR/rebase_resume_state
+
+REMAINING_STEPS=$"
+The rebase process is complete.  The following steps must be completed manually:
+  ./mach bootstrap --application=browser --no-system-changes
+  ./mach build
+  hg push -r tip --force
+  hg push -B $MOZ_BOOKMARK
+"
+echo "$REMAINING_STEPS"
diff --git a/dom/media/webrtc/third_party_build/extract-for-git.py b/dom/media/webrtc/third_party_build/extract-for-git.py
new file mode 100644
index 0000000000..d2701d7dff
--- /dev/null
+++ b/dom/media/webrtc/third_party_build/extract-for-git.py
@@ -0,0 +1,145 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+import argparse
+import os
+import re
+import subprocess
+
+# This script extracts commits that touch third party webrtc code so they can
+# be imported into Git. It filters out commits that are not part of upstream
+# code and rewrites the paths to match upstream. Finally, the commits are
+# combined into a mailbox file that can be applied with `git am`.
+LIBWEBRTC_DIR = "third_party/libwebrtc"
+
+
+def build_commit_list(revset, env):
+    """Build commit list from the specified revset.
+
+    The revset can be a single revision, e.g. 52bb9bb94661, or a range,
+    e.g. 8c08a5bb8a99::52bb9bb94661, or any other valid revset
+    (check hg help revset). Only commits that touch libwebrtc are included.
+    """
+    res = subprocess.run(
+        ["hg", "log", "-r", revset, "-M", "--template", "{node}\n", LIBWEBRTC_DIR],
+        capture_output=True,
+        text=True,
+        env=env,
+    )
+    return [line.strip() for line in res.stdout.strip().split("\n")]
+
+
+def extract_author_date(sha1, env):
+    res = subprocess.run(
+        ["hg", "log", "-r", sha1, "--template", "{author}|{date|isodate}"],
+        capture_output=True,
+        text=True,
+        env=env,
+    )
+    return res.stdout.split("|")
+
+
+def extract_description(sha1, env):
+    res = subprocess.run(
+        ["hg", "log", "-r", sha1, "--template", "{desc}"],
+        capture_output=True,
+        text=True,
+        env=env,
+    )
+    return res.stdout
+
+
+def extract_commit(sha1, env):
+    res = subprocess.run(
+        ["hg", "log", "-r", sha1, "-pg", "--template", "\n"],
+        capture_output=True,
+        text=True,
+        env=env,
+    )
+    return res.stdout
+
+
+def filter_nonwebrtc(commit):
+    filtered = []
+    skipping = False
+    for line in commit.split("\n"):
+        # Extract only patches affecting libwebrtc, but avoid commits that
+        # touch build, which is tracked by a separate repo, or that affect
+        # moz.build files which are code generated.
+        if (
+            line.startswith("diff --git a/" + LIBWEBRTC_DIR)
+            and not line.startswith("diff --git a/" + LIBWEBRTC_DIR + "/build")
+            and not line.startswith("diff --git a/" + LIBWEBRTC_DIR + "/third_party")
+            and not line.startswith(
+                "diff --git a/" + LIBWEBRTC_DIR + "/moz-patch-stack"
+            )
+            and not line.endswith("moz.build")
+        ):
+            skipping = False
+        elif line.startswith("diff --git"):
+            skipping = True
+
+        if not skipping:
+            filtered.append(line)
+    return "\n".join(filtered)
+
+
+def fixup_paths(commit):
+    # make sure we only rewrite paths in the diff-related or rename lines
+    commit = re.sub(
+        f"^rename (from|to) {LIBWEBRTC_DIR}/", "rename \\1 ", commit, flags=re.MULTILINE
+    )
+    return re.sub(f"( [ab])/{LIBWEBRTC_DIR}/", "\\1/", commit)
+
+
+def write_as_mbox(sha1, author, date, description, commit, ofile):
+    # Use same magic date as git format-patch
+    ofile.write("From {} Mon Sep 17 00:00:00 2001\n".format(sha1))
+    ofile.write("From: {}\n".format(author))
+    ofile.write("Date: {}\n".format(date))
+    description = description.split("\n")
+    ofile.write("Subject: {}\n".format(description[0]))
+    ofile.write("\n".join(description[1:]))
+    ofile.write(
+        "\nMercurial Revision: https://hg.mozilla.org/mozilla-central/rev/{}\n".format(
+            sha1
+        )
+    )
+    ofile.write(commit)
+    ofile.write("\n")
+    ofile.write("\n")
+
+
+if __name__ == "__main__":
+    commits = []
+    parser = argparse.ArgumentParser(
+        description="Format commits for upstream libwebrtc"
+    )
+    parser.add_argument(
+        "revsets", metavar="revset", type=str, nargs="+", help="A revset to process"
+    )
+    parser.add_argument(
+        "--target", choices=("libwebrtc", "build", "third_party"), default="libwebrtc"
+    )
+    args = parser.parse_args()
+
+    if args.target != "libwebrtc":
+        LIBWEBRTC_DIR = os.path.join(LIBWEBRTC_DIR, args.target)
+
+    # must run 'hg' with HGPLAIN=1 to ensure aliases don't interfere with
+    # command output.
+    env = os.environ.copy()
+    env["HGPLAIN"] = "1"
+
+    for revset in args.revsets:
+        commits.extend(build_commit_list(revset, env))
+
+    with open("mailbox.patch", "w") as ofile:
+        for sha1 in commits:
+            author, date = extract_author_date(sha1, env)
+            description = extract_description(sha1, env)
+            filtered_commit = filter_nonwebrtc(extract_commit(sha1, env))
+            if len(filtered_commit) == 0:
+                continue
+            fixedup_commit = fixup_paths(filtered_commit)
+            write_as_mbox(sha1, author, date, description, fixedup_commit, ofile)
diff --git a/dom/media/webrtc/third_party_build/fast-forward-libwebrtc.sh b/dom/media/webrtc/third_party_build/fast-forward-libwebrtc.sh
new file mode 100644
index 0000000000..9ef40a41ac
--- /dev/null
+++ b/dom/media/webrtc/third_party_build/fast-forward-libwebrtc.sh
@@ -0,0 +1,256 @@
+#!/bin/bash
+
+function show_error_msg()
+{
+  echo "*** ERROR *** $? line $1 $0 did not complete successfully!"
+  echo "$ERROR_HELP"
+}
+ERROR_HELP=""
+
+# Print an Error message if `set -eE` causes the script to exit due to a failed command
+trap 'show_error_msg $LINENO' ERR
+
+source dom/media/webrtc/third_party_build/use_config_env.sh
+
+# If DEBUG_GEN is set all commands should be printed as they are executed
+if [ ! "x$DEBUG_GEN" = "x" ]; then
+  set -x
+fi
+
+if [ "x$MOZ_LIBWEBRTC_SRC" = "x" ]; then
+  echo "MOZ_LIBWEBRTC_SRC is not defined, see README.md"
+  exit
+fi
+
+if [ -d $MOZ_LIBWEBRTC_SRC ]; then
+  echo "MOZ_LIBWEBRTC_SRC is $MOZ_LIBWEBRTC_SRC"
+else
+  echo "Path $MOZ_LIBWEBRTC_SRC is not found, see README.md"
+  exit
+fi
+
+if [ "x$MOZ_LIBWEBRTC_BRANCH" = "x" ]; then
+  echo "MOZ_LIBWEBRTC_BRANCH is not defined, see README.md"
+  exit
+fi
+
+if [ "x$HANDLE_NOOP_COMMIT" = "x" ]; then
+  HANDLE_NOOP_COMMIT=""
+fi
+
+RESUME=""
+if [ -f $STATE_DIR/resume_state ]; then
+  RESUME=`tail -1 $STATE_DIR/resume_state`
+fi
+
+GIT_IS_REBASING=`cd $MOZ_LIBWEBRTC_SRC && git status | grep "interactive rebase in progress" | wc -l | tr -d " " || true`
+if [ "x$GIT_IS_REBASING" != "x0" ]; then
+  echo "There is currently a git rebase operation in progress at $MOZ_LIBWEBRTC_SRC."
+  echo "Please resolve the rebase before attempting to continue the fast-forward"
+  echo "operation."
+  exit 1
+fi
+
+if [ "x$RESUME" = "x" ]; then
+  SKIP_TO="run"
+  # Check for modified files and abort if present.
+  MODIFIED_FILES=`hg status --exclude "third_party/libwebrtc/**.orig" third_party/libwebrtc`
+  if [ "x$MODIFIED_FILES" = "x" ]; then
+    # Completely clean the mercurial checkout before proceeding
+    hg update -C -r .
+    hg purge
+  else
+    echo "There are modified files in the checkout. Cowardly aborting!"
+    echo "$MODIFIED_FILES"
+    exit 1
+  fi
+else
+  SKIP_TO=$RESUME
+  hg revert -C third_party/libwebrtc/README.moz-ff-commit &> /dev/null
+fi
+
+find_base_commit
+find_next_commit
+
+echo "looking for $STATE_DIR/$MOZ_LIBWEBRTC_NEXT_BASE.no-op-cherry-pick-msg"
+if [ -f $STATE_DIR/$MOZ_LIBWEBRTC_NEXT_BASE.no-op-cherry-pick-msg ]; then
+  echo "***"
+  echo "*** detected special commit msg, setting HANDLE_NOOP_COMMIT"
+  echo "***"
+  HANDLE_NOOP_COMMIT="1"
+fi
+
+UPSTREAM_ADDED_FILES=""
+
+# Grab the filtered changes from git based on what we vendor.
+FILTERED_GIT_CHANGES=`./mach python $SCRIPT_DIR/filter_git_changes.py \
+   --repo-path $MOZ_LIBWEBRTC_SRC --commit-sha $MOZ_LIBWEBRTC_NEXT_BASE`
+
+# After this point:
+# * eE: All commands should succeed.
+# * u: All variables should be defined before use.
+# * o pipefail: All stages of all pipes should succeed.
+set -eEuo pipefail
+
+echo "     MOZ_LIBWEBRTC_BASE: $MOZ_LIBWEBRTC_BASE"
+echo "MOZ_LIBWEBRTC_NEXT_BASE: $MOZ_LIBWEBRTC_NEXT_BASE"
+echo "HANDLE_NOOP_COMMIT: $HANDLE_NOOP_COMMIT"
+echo " RESUME: $RESUME"
+echo "SKIP_TO: $SKIP_TO"
+
+echo "-------"
+echo "------- Write cmd-line to third_party/libwebrtc/README.moz-ff-commit"
+echo "-------"
+echo "# MOZ_LIBWEBRTC_SRC=$MOZ_LIBWEBRTC_SRC MOZ_LIBWEBRTC_BRANCH=$MOZ_LIBWEBRTC_BRANCH bash $0" \
+    >> third_party/libwebrtc/README.moz-ff-commit
+
+echo "-------"
+echo "------- Write new-base to last line of third_party/libwebrtc/README.moz-ff-commit"
+echo "-------"
+echo "# base of lastest vendoring" >> third_party/libwebrtc/README.moz-ff-commit
+echo "$MOZ_LIBWEBRTC_NEXT_BASE" >> third_party/libwebrtc/README.moz-ff-commit
+
+REBASE_HELP=$"
+The rebase operation onto $MOZ_LIBWEBRTC_NEXT_BASE has failed.  Please
+resolve all the rebase conflicts.  To fix this issue, you will need to
+jump to the github repo at $MOZ_LIBWEBRTC_SRC .
+When the github rebase is complete, re-run the script to resume the
+fast-forward process.
+"
+#"rebase_mozlibwebrtc_stack help for rebase failure"
+function rebase_mozlibwebrtc_stack {
+  echo "-------"
+  echo "------- Rebase $MOZ_LIBWEBRTC_BRANCH to $MOZ_LIBWEBRTC_NEXT_BASE"
+  echo "-------"
+  ERROR_HELP=$REBASE_HELP
+  ( cd $MOZ_LIBWEBRTC_SRC && \
+    git checkout -q $MOZ_LIBWEBRTC_BRANCH && \
+    git rebase $MOZ_LIBWEBRTC_NEXT_BASE \
+    &> $LOG_DIR/log-rebase-moz-libwebrtc.txt \
+  )
+  ERROR_HELP=""
+}
+
+function vendor_off_next_commit {
+  echo "-------"
+  echo "------- Vendor $MOZ_LIBWEBRTC_BRANCH from $MOZ_LIBWEBRTC_SRC"
+  echo "-------"
+  ./mach python $SCRIPT_DIR/vendor-libwebrtc.py \
+            --from-local $MOZ_LIBWEBRTC_SRC \
+            --commit $MOZ_LIBWEBRTC_BRANCH \
+            libwebrtc
+}
+
+# The vendoring script (called above in vendor_off_next_commit) replaces
+# the entire third_party/libwebrtc directory, which effectively removes
+# all the generated moz.build files.  It is easier (less error prone),
+# to revert only those missing moz.build files rather than attempt to
+# rebuild them because the rebuild may need json updates to work properly.
+function regen_mozbuild_files {
+  echo "-------"
+  echo "------- Restore moz.build files from repo"
+  echo "-------"
+  hg revert --include "third_party/libwebrtc/**moz.build" \
+    third_party/libwebrtc &> $LOG_DIR/log-regen-mozbuild-files.txt
+}
+
+function add_new_upstream_files {
+  if [ "x$HANDLE_NOOP_COMMIT" == "x1" ]; then
+    return
+  fi
+  UPSTREAM_ADDED_FILES=`echo "$FILTERED_GIT_CHANGES" | grep "^A" \
+      | awk '{print $2;}' || true`
+  if [ "x$UPSTREAM_ADDED_FILES" != "x" ]; then
+    echo "-------"
+    echo "------- Add new upstream files"
+    echo "-------"
+    (cd third_party/libwebrtc && hg add $UPSTREAM_ADDED_FILES)
+    echo "$UPSTREAM_ADDED_FILES" &> $LOG_DIR/log-new-upstream-files.txt
+  fi
+}
+
+function remove_deleted_upstream_files {
+  if [ "x$HANDLE_NOOP_COMMIT" == "x1" ]; then
+    return
+  fi
+  UPSTREAM_DELETED_FILES=`echo "$FILTERED_GIT_CHANGES" | grep "^D" \
+      | awk '{print $2;}' || true`
+  if [ "x$UPSTREAM_DELETED_FILES" != "x" ]; then
+    echo "-------"
+    echo "------- Remove deleted upstream files"
+    echo "-------"
+    (cd third_party/libwebrtc && hg rm $UPSTREAM_DELETED_FILES)
+    echo "$UPSTREAM_DELETED_FILES" &> $LOG_DIR/log-deleted-upstream-files.txt
+  fi
+}
+
+function handle_renamed_upstream_files {
+  if [ "x$HANDLE_NOOP_COMMIT" == "x1" ]; then
+    return
+  fi
+  UPSTREAM_RENAMED_FILES=`echo "$FILTERED_GIT_CHANGES" | grep "^R" \
+      | awk '{print $2 " " $3;}' || true`
+  if [ "x$UPSTREAM_RENAMED_FILES" != "x" ]; then
+    echo "-------"
+    echo "------- Handle renamed upstream files"
+    echo "-------"
+    (cd third_party/libwebrtc && echo "$UPSTREAM_RENAMED_FILES" | while read line; do hg rename --after $line; done)
+    echo "$UPSTREAM_RENAMED_FILES" &> $LOG_DIR/log-renamed-upstream-files.txt
+  fi
+}
+
+if [ $SKIP_TO = "run" ]; then
+  echo "resume2" > $STATE_DIR/resume_state
+  rebase_mozlibwebrtc_stack;
+fi
+
+if [ $SKIP_TO = "resume2" ]; then SKIP_TO="run"; fi
+if [ $SKIP_TO = "run" ]; then
+  echo "resume3" > $STATE_DIR/resume_state
+  vendor_off_next_commit;
+fi
+
+if [ $SKIP_TO = "resume3" ]; then SKIP_TO="run"; fi
+if [ $SKIP_TO = "run" ]; then
+  echo "resume4" > $STATE_DIR/resume_state
+  regen_mozbuild_files;
+fi
+
+if [ $SKIP_TO = "resume4" ]; then SKIP_TO="run"; fi
+if [ $SKIP_TO = "run" ]; then
+  echo "resume5" > $STATE_DIR/resume_state
+  remove_deleted_upstream_files;
+fi
+
+if [ $SKIP_TO = "resume5" ]; then SKIP_TO="run"; fi
+if [ $SKIP_TO = "run" ]; then
+  echo "resume6" > $STATE_DIR/resume_state
+  add_new_upstream_files;
+fi
+
+if [ $SKIP_TO = "resume6" ]; then SKIP_TO="run"; fi
+if [ $SKIP_TO = "run" ]; then
+  echo "resume7" > $STATE_DIR/resume_state
+  handle_renamed_upstream_files;
+fi
+
+echo "" > $STATE_DIR/resume_state
+echo "-------"
+echo "------- Commit vendored changes from $MOZ_LIBWEBRTC_NEXT_BASE"
+echo "-------"
+UPSTREAM_SHA=`cd $MOZ_LIBWEBRTC_SRC && \
+    git show --name-only $MOZ_LIBWEBRTC_NEXT_BASE \
+    | grep "^commit " | awk '{ print $NF }'`
+echo "Bug $MOZ_FASTFORWARD_BUG - Vendor libwebrtc from $MOZ_LIBWEBRTC_NEXT_BASE" \
+    > $TMP_DIR/commit_msg.txt
+echo "" >> $TMP_DIR/commit_msg.txt
+if [ -f $STATE_DIR/$MOZ_LIBWEBRTC_NEXT_BASE.no-op-cherry-pick-msg ]; then
+  cat $STATE_DIR/$MOZ_LIBWEBRTC_NEXT_BASE.no-op-cherry-pick-msg >> $TMP_DIR/commit_msg.txt
+  echo "" >> $TMP_DIR/commit_msg.txt
+  rm $STATE_DIR/$MOZ_LIBWEBRTC_NEXT_BASE.no-op-cherry-pick-msg
+fi
+echo "Upstream commit: https://webrtc.googlesource.com/src/+/$UPSTREAM_SHA" >> $TMP_DIR/commit_msg.txt
+(cd $MOZ_LIBWEBRTC_SRC && \
+git show --name-only $MOZ_LIBWEBRTC_NEXT_BASE | grep "^ ") >> $TMP_DIR/commit_msg.txt
+
+hg commit -l $TMP_DIR/commit_msg.txt third_party/libwebrtc
diff --git a/dom/media/webrtc/third_party_build/fetch_github_repo.py b/dom/media/webrtc/third_party_build/fetch_github_repo.py
new file mode 100644
index 0000000000..bfa40f5c7b
--- /dev/null
+++ b/dom/media/webrtc/third_party_build/fetch_github_repo.py
@@ -0,0 +1,122 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+import argparse
+import os
+import re
+import shutil
+
+from run_operations import run_git, run_shell
+
+# This script fetches the moz-libwebrtc github repro with the expected
+# upstream remote and branch-heads setup.  This is used by both the
+# prep_repo.sh script as well as the restore_patch_stack.py script.
+#
+# For speed and conservation of network resources, after fetching all
+# the data, a tar of the repo is made and used if available.
+
+
+def fetch_repo(github_path, force_fetch, tar_path):
+    capture_output = False
+
+    # check for pre-existing repo - make sure we force the removal
+    if force_fetch and os.path.exists(github_path):
+        print("Removing existing repo: {}".format(github_path))
+        shutil.rmtree(github_path)
+
+    # clone https://github.com/mozilla/libwebrtc
+    if not os.path.exists(github_path):
+        # check for pre-existing tar, use it if we have it
+        if os.path.exists(tar_path):
+            print("Using tar file to reconstitute repo")
+            cmd = "cd {} ; tar --extract --gunzip --file={}".format(
+                os.path.dirname(github_path), os.path.basename(tar_path)
+            )
+            run_shell(cmd, capture_output)
+        else:
+            print("Cloning github repo")
+            run_shell(
+                "git clone https://github.com/mozilla/libwebrtc {}".format(github_path),
+                capture_output,
+            )
+
+    # setup upstream (https://webrtc.googlesource.com/src)
+    stdout_lines = run_git("git config --local --list", github_path)
+    stdout_lines = [
+        path for path in stdout_lines if re.findall("^remote.upstream.url.*", path)
+    ]
+    if len(stdout_lines) == 0:
+        print("Fetching upstream")
+        run_git("git checkout master", github_path)
+        run_git(
+            "git remote add upstream https://webrtc.googlesource.com/src", github_path
+        )
+        run_git("git fetch upstream", github_path)
+        run_git("git merge upstream/master", github_path)
+    else:
+        print(
+            "Upstream remote (https://webrtc.googlesource.com/src) already configured"
+        )
+
+    # setup upstream branch-heads
+    stdout_lines = run_git(
+        "git config --local --get-all remote.upstream.fetch", github_path
+    )
+    if len(stdout_lines) == 1:
+        print("Fetching upstream branch-heads")
+        run_git(
+            "git config --local --add remote.upstream.fetch +refs/branch-heads/*:refs/remotes/branch-heads/*",
+            github_path,
+        )
+        run_git("git fetch upstream", github_path)
+    else:
+        print("Upstream remote branch-heads already configured")
+
+    # do a sanity fetch in case this was not a freshly cloned copy of the
+    # repo, meaning it may not have all the mozilla branches present.
+    run_git("git fetch --all", github_path)
+
+    # create tar to avoid time refetching
+    if not os.path.exists(tar_path):
+        print("Creating tar file for quicker restore")
+        cmd = "cd {} ; tar --create --gzip --file={} {}".format(
+            os.path.dirname(github_path),
+            os.path.basename(tar_path),
+            os.path.basename(github_path),
+        )
+        run_shell(cmd, capture_output)
+
+
+if __name__ == "__main__":
+    default_state_dir = ".moz-fast-forward"
+    default_tar_name = "moz-libwebrtc.tar.gz"
+
+    parser = argparse.ArgumentParser(
+        description="Restore moz-libwebrtc github patch stack"
+    )
+    parser.add_argument(
+        "--repo-path",
+        required=True,
+        help="path to libwebrtc repo",
+    )
+    parser.add_argument(
+        "--force-fetch",
+        action="store_true",
+        default=False,
+        help="force rebuild an existing repo directory",
+    )
+    parser.add_argument(
+        "--tar-name",
+        default=default_tar_name,
+        help="name of tar file (defaults to {})".format(default_tar_name),
+    )
+    parser.add_argument(
+        "--state-path",
+        default=default_state_dir,
+        help="path to state directory (defaults to {})".format(default_state_dir),
+    )
+    args = parser.parse_args()
+
+    fetch_repo(
+        args.repo_path, args.force_fetch, os.path.join(args.state_path, args.tar_name)
+    )
diff --git a/dom/media/webrtc/third_party_build/filter_git_changes.py b/dom/media/webrtc/third_party_build/filter_git_changes.py
new file mode 100644
index 0000000000..f8964e145b
--- /dev/null
+++ b/dom/media/webrtc/third_party_build/filter_git_changes.py
@@ -0,0 +1,72 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+import argparse
+import importlib
+import re
+import subprocess
+import sys
+
+sys.path.insert(0, "./dom/media/webrtc/third_party_build")
+vendor_libwebrtc = importlib.import_module("vendor-libwebrtc")
+
+if __name__ == "__main__":
+    parser = argparse.ArgumentParser(
+        description="Get relevant change count from an upstream git commit"
+    )
+    parser.add_argument(
+        "--repo-path",
+        required=True,
+        help="path to libwebrtc repo",
+    )
+    parser.add_argument("--commit-sha", required=True, help="sha of commit to examine")
+    parser.add_argument("--diff-filter", choices=("A", "D", "R"))
+    args = parser.parse_args()
+
+    command = [
+        "git",
+        "show",
+        "--oneline",
+        "--name-status",
+        "--pretty=format:",
+        None if not args.diff_filter else "--diff-filter={}".format(args.diff_filter),
+        args.commit_sha,
+    ]
+    # strip possible empty elements from command list
+    command = [x for x in command if x is not None]
+
+    # Get the list of changes in the upstream commit.
+    res = subprocess.run(
+        command,
+        capture_output=True,
+        text=True,
+        cwd=args.repo_path,
+    )
+    if res.returncode != 0:
+        sys.exit("error: {}".format(res.stderr.strip()))
+
+    changed_files = [line.strip() for line in res.stdout.strip().split("\n")]
+    changed_files = [line for line in changed_files if line != ""]
+
+    # Fetch the list of excludes and includes used in the vendoring script.
+    exclude_list = vendor_libwebrtc.get_excluded_paths()
+    include_list = vendor_libwebrtc.get_included_path_overrides()
+
+    # First, search for changes in files that are specifically included.
+    # Do this first, because some of these files might be filtered out
+    # by the exclude list.
+    regex_includes = "|".join(["^.\t{}".format(i) for i in include_list])
+    included_files = [
+        path for path in changed_files if re.findall(regex_includes, path)
+    ]
+
+    # Convert the exclude list to a regex string.
+    regex_excludes = "|".join(["^.\t{}".format(i) for i in exclude_list])
+
+    # Filter out the excluded files/paths.
+    files_not_excluded = [
+        path for path in changed_files if not re.findall(regex_excludes, path)
+    ]
+
+    for path in included_files + files_not_excluded:
+        print(path)
diff --git a/dom/media/webrtc/third_party_build/gn-configs/README.md b/dom/media/webrtc/third_party_build/gn-configs/README.md
new file mode 100644
index 0000000000..111d2d022e
--- /dev/null
+++ b/dom/media/webrtc/third_party_build/gn-configs/README.md
@@ -0,0 +1,16 @@
+# Generate new gn json files and moz.build files for building libwebrtc in our tree
+
+/!\ This is only supported on Linux and macOS. If you are on Windows, you can run
+the script under [WSL](https://docs.microsoft.com/en-us/windows/wsl/install).
+
+1. The script should be run from the top directory of our firefox tree.
+
+   ```
+   ./mach python python/mozbuild/mozbuild/gn_processor.py dom/media/webrtc/third_party_build/gn-configs/webrtc.json
+   ```
+
+2. Checkin all the generated/modified files and try your build!
+
+# Adding new configurations to the build
+
+Edit the `main` function in the `python/mozbuild/mozbuild/gn_processor.py` file.
diff --git a/dom/media/webrtc/third_party_build/gn-configs/webrtc.json b/dom/media/webrtc/third_party_build/gn-configs/webrtc.json
new file mode 100644
index 0000000000..9744558025
--- /dev/null
+++ b/dom/media/webrtc/third_party_build/gn-configs/webrtc.json
@@ -0,0 +1,83 @@
+{
+  "target_dir": "third_party/libwebrtc",
+  "gn_target": "//:webrtc",
+  "gn_sandbox_variables": {
+    "COMPILE_FLAGS": {
+      "WARNINGS_AS_ERRORS": []
+    },
+    "FINAL_LIBRARY": "webrtc"
+  },
+  "mozilla_flags": ["-fobjc-arc", "-mavx2", "-mfma", "-mfpu=neon", "-msse2"],
+  "write_mozbuild_variables": {
+    "INCLUDE_TK_CFLAGS_DIRS": [
+      "third_party/libwebrtc/modules/desktop_capture/desktop_capture_gn",
+      "third_party/libwebrtc/modules/portal/portal_gn"
+    ]
+  },
+  "non_unified_sources": [
+    "third_party/libwebrtc/api/audio_codecs/opus/audio_encoder_opus_config.cc",
+    "third_party/libwebrtc/api/video/i210_buffer.cc",
+    "third_party/libwebrtc/api/video/i410_buffer.cc",
+    "third_party/libwebrtc/api/video/i422_buffer.cc",
+    "third_party/libwebrtc/api/video/i444_buffer.cc",
+    "third_party/libwebrtc/audio/channel_send_frame_transformer_delegate.cc",
+    "third_party/libwebrtc/common_audio/vad/vad_core.c",
+    "third_party/libwebrtc/common_audio/vad/webrtc_vad.c",
+    "third_party/libwebrtc/common_audio/signal_processing/resample_by_2_mips.c",
+    "third_party/libwebrtc/modules/audio_coding/codecs/isac/fix/source/decode_plc.c",
+    "third_party/libwebrtc/modules/audio_coding/codecs/isac/fix/source/lpc_masking_model.c",
+    "third_party/libwebrtc/modules/audio_coding/codecs/isac/fix/source/pitch_filter.c",
+    "third_party/libwebrtc/modules/audio_coding/codecs/isac/fix/source/pitch_filter_c.c",
+    "third_party/libwebrtc/modules/audio_coding/neteq/audio_vector.cc",
+    "third_party/libwebrtc/modules/audio_coding/neteq/underrun_optimizer.cc",
+    "third_party/libwebrtc/modules/audio_device/android/audio_manager.cc",
+    "third_party/libwebrtc/modules/audio_device/android/audio_record_jni.cc",
+    "third_party/libwebrtc/modules/audio_device/android/audio_track_jni.cc",
+    "third_party/libwebrtc/modules/audio_device/android/opensles_player.cc",
+    "third_party/libwebrtc/modules/audio_device/linux/audio_device_pulse_linux.cc",
+    "third_party/libwebrtc/modules/audio_device/linux/audio_mixer_manager_pulse_linux.cc",
+    "third_party/libwebrtc/modules/audio_device/win/audio_device_core_win.cc",
+    "third_party/libwebrtc/modules/audio_processing/aecm/aecm_core.cc",
+    "third_party/libwebrtc/modules/audio_processing/aecm/aecm_core_c.cc",
+    "third_party/libwebrtc/modules/audio_processing/aecm/aecm_core_mips.cc",
+    "third_party/libwebrtc/modules/audio_processing/aecm/aecm_core_neon.cc",
+    "third_party/libwebrtc/modules/audio_processing/aecm/echo_control_mobile.cc",
+    "third_party/libwebrtc/modules/audio_processing/echo_control_mobile_impl.cc",
+    "third_party/libwebrtc/modules/audio_processing/echo_detector/normalized_covariance_estimator.cc",
+    "third_party/libwebrtc/modules/audio_processing/gain_control_impl.cc",
+    "third_party/libwebrtc/modules/audio_processing/rms_level.cc",
+    "third_party/libwebrtc/modules/congestion_controller/goog_cc/loss_based_bandwidth_estimation.cc",
+    "third_party/libwebrtc/modules/congestion_controller/goog_cc/send_side_bandwidth_estimation.cc",
+    "third_party/libwebrtc/modules/desktop_capture/fallback_desktop_capturer_wrapper.cc",
+    "third_party/libwebrtc/modules/desktop_capture/linux/wayland/base_capturer_pipewire.cc",
+    "third_party/libwebrtc/modules/desktop_capture/linux/wayland/moz_base_capturer_pipewire.cc",
+    "third_party/libwebrtc/modules/desktop_capture/mouse_cursor_monitor_linux.cc",
+    "third_party/libwebrtc/modules/desktop_capture/win/screen_capturer_win_gdi.cc",
+    "third_party/libwebrtc/modules/pacing/prioritized_packet_queue.cc",
+    "third_party/libwebrtc/modules/remote_bitrate_estimator/remote_bitrate_estimator_single_stream.cc",
+    "third_party/libwebrtc/modules/rtp_rtcp/source/flexfec_receiver.cc",
+    "third_party/libwebrtc/modules/rtp_rtcp/source/rtcp_packet/tmmbn.cc",
+    "third_party/libwebrtc/modules/rtp_rtcp/source/rtcp_packet/tmmbr.cc",
+    "third_party/libwebrtc/modules/rtp_rtcp/source/rtcp_sender.cc",
+    "third_party/libwebrtc/modules/rtp_rtcp/source/rtp_format_vp8.cc",
+    "third_party/libwebrtc/modules/rtp_rtcp/source/rtp_rtcp_impl2.cc",
+    "third_party/libwebrtc/modules/rtp_rtcp/source/rtp_sender_egress.cc",
+    "third_party/libwebrtc/modules/rtp_rtcp/source/rtp_sender_video.cc",
+    "third_party/libwebrtc/modules/rtp_rtcp/source/rtp_util.cc",
+    "third_party/libwebrtc/modules/rtp_rtcp/source/ulpfec_generator.cc",
+    "third_party/libwebrtc/modules/rtp_rtcp/source/video_rtp_depacketizer_vp9.cc",
+    "third_party/libwebrtc/modules/third_party/g722/g722_encode.c",
+    "third_party/libwebrtc/modules/video_capture/windows/device_info_ds.cc",
+    "third_party/libwebrtc/modules/video_capture/windows/help_functions_ds.cc",
+    "third_party/libwebrtc/modules/video_capture/windows/sink_filter_ds.cc",
+    "third_party/libwebrtc/modules/video_coding/codecs/vp8/screenshare_layers.cc",
+    "third_party/libwebrtc/modules/video_coding/svc/scalability_structure_key_svc.cc",
+    "third_party/libwebrtc/modules/video_coding/svc/scalability_structure_simulcast.cc",
+    "third_party/libwebrtc/rtc_base/win/hstring.cc",
+    "third_party/libwebrtc/third_party/abseil-cpp/absl/strings/numbers.cc",
+    "third_party/libwebrtc/third_party/abseil-cpp/absl/synchronization/blocking_counter.cc",
+    "third_party/libwebrtc/third_party/abseil-cpp/absl/time/internal/cctz/src/time_zone_posix.cc",
+    "third_party/libwebrtc/third_party/abseil-cpp/absl/time/time.cc",
+    "third_party/libwebrtc/video/rtp_video_stream_receiver2.cc"
+  ]
+}
diff --git a/dom/media/webrtc/third_party_build/lookup_branch_head.py b/dom/media/webrtc/third_party_build/lookup_branch_head.py
new file mode 100644
index 0000000000..afd0e6c791
--- /dev/null
+++ b/dom/media/webrtc/third_party_build/lookup_branch_head.py
@@ -0,0 +1,98 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+import argparse
+import json
+import os
+import pathlib
+import sys
+import urllib.request
+
+# default cache file location in STATE_DIR location
+default_cache_path = ".moz-fast-forward/milestone.cache"
+
+
+def fetch_branch_head_dict():
+    milestone_url = (
+        "https://chromiumdash.appspot.com/fetch_milestones?only_branched=true"
+    )
+    uf = urllib.request.urlopen(milestone_url)
+    html = uf.read()
+    milestone_dict = json.loads(html)
+
+    # There is more information in the json dictionary, but we only care
+    # about the milestone (version) to branch "name" (webrtc_branch)
+    # info.  For example:
+    #  v106 -> 5249 (which translates to branch-heads/5249)
+    #  v107 -> 5304 (which translates to branch-heads/5304)
+    #
+    # As returned from web query, milestones are integers and branch
+    # "names" are strings.
+    new_dict = {}
+    for row in milestone_dict:
+        new_dict[row["milestone"]] = row["webrtc_branch"]
+
+    return new_dict
+
+
+def read_dict_from_cache(cache_path):
+    if cache_path is not None and os.path.exists(cache_path):
+        with open(cache_path, "r") as ifile:
+            return json.loads(ifile.read(), object_hook=jsonKeys2int)
+    return {}
+
+
+def write_dict_to_cache(cache_path, milestones):
+    with open(cache_path, "w") as ofile:
+        ofile.write(json.dumps(milestones))
+
+
+def get_branch_head(milestone, cache_path=default_cache_path):
+    milestones = read_dict_from_cache(cache_path)
+
+    # if the cache didn't exist or is stale, try to fetch using a web query
+    if milestone not in milestones:
+        try:
+            milestones = fetch_branch_head_dict()
+            write_dict_to_cache(cache_path, milestones)
+        except Exception:
+            pass
+
+    if milestone in milestones:
+        return milestones[milestone]
+    return None
+
+
+# From https://stackoverflow.com/questions/1450957/pythons-json-module-converts-int-dictionary-keys-to-strings
+def jsonKeys2int(x):
+    if isinstance(x, dict):
+        return {int(k): v for k, v in x.items()}
+    return x
+
+
+if __name__ == "__main__":
+    parser = argparse.ArgumentParser(
+        description="Get libwebrtc branch-head for given chromium milestone"
+    )
+    parser.add_argument(
+        "milestone", type=int, help="integer chromium milestone (example: 106)"
+    )
+    parser.add_argument("-v", "--verbose", action="store_true")
+    parser.add_argument("-c", "--cache", type=pathlib.Path, help="path to cache file")
+    args = parser.parse_args()
+
+    # if the user provided a cache path use it, otherwise use the default
+    local_cache_path = args.cache or default_cache_path
+
+    branch_head = get_branch_head(args.milestone, local_cache_path)
+    if branch_head is None:
+        sys.exit("error: chromium milestone '{}' is not found.".format(args.milestone))
+
+    if args.verbose:
+        print(
+            "chromium milestone {} uses branch-heads/{}".format(
+                args.milestone, branch_head
+            )
+        )
+    else:
+        print(branch_head)
diff --git a/dom/media/webrtc/third_party_build/loop-ff.sh b/dom/media/webrtc/third_party_build/loop-ff.sh
new file mode 100644
index 0000000000..72a8d88091
--- /dev/null
+++ b/dom/media/webrtc/third_party_build/loop-ff.sh
@@ -0,0 +1,236 @@
+#!/bin/bash
+
+source dom/media/webrtc/third_party_build/use_config_env.sh
+
+# file for logging loop script output
+LOOP_OUTPUT_LOG=$LOG_DIR/log-loop-ff.txt
+
+function echo_log()
+{
+  echo "===loop-ff=== $@" 2>&1| tee -a $LOOP_OUTPUT_LOG
+}
+
+function show_error_msg()
+{
+  echo_log "*** ERROR *** $? line $1 $0 did not complete successfully!"
+  echo_log "$ERROR_HELP"
+}
+ERROR_HELP=""
+
+# Print an Error message if `set -eE` causes the script to exit due to a failed command
+trap 'show_error_msg $LINENO' ERR
+
+# If DEBUG_LOOP_FF is set all commands should be printed as they are executed
+if [ ! "x$DEBUG_LOOP_FF" = "x" ]; then
+  set -x
+fi
+
+if [ "x$MOZ_LIBWEBRTC_SRC" = "x" ]; then
+  echo "MOZ_LIBWEBRTC_SRC is not defined, see README.md"
+  exit
+fi
+
+if [ ! -d $MOZ_LIBWEBRTC_SRC ]; then
+  echo "Path $MOZ_LIBWEBRTC_SRC is not found, see README.md"
+  exit
+fi
+
+if [ "x$MOZ_LIBWEBRTC_BRANCH" = "x" ]; then
+  echo "MOZ_LIBWEBRTC_BRANCH is not defined, see README.md"
+  exit
+fi
+
+if [ "x$MOZ_STOP_AFTER_COMMIT" = "x" ]; then
+  MOZ_STOP_AFTER_COMMIT=`cd $MOZ_LIBWEBRTC_SRC ; git show $MOZ_TARGET_UPSTREAM_BRANCH_HEAD --format='%h' --name-only | head -1`
+  echo "No MOZ_STOP_AFTER_COMMIT variable defined - stopping at $MOZ_TARGET_UPSTREAM_BRANCH_HEAD"
+fi
+
+if [ "x$MOZ_ADVANCE_ONE_COMMIT" = "x" ]; then
+  MOZ_ADVANCE_ONE_COMMIT=""
+fi
+
+if [ "x$SKIP_NEXT_REVERT_CHK" = "x" ]; then
+  SKIP_NEXT_REVERT_CHK="0"
+fi
+
+MOZ_CHANGED=0
+GIT_CHANGED=0
+HANDLE_NOOP_COMMIT=""
+
+# After this point:
+# * eE: All commands should succeed.
+# * u: All variables should be defined before use.
+# * o pipefail: All stages of all pipes should succeed.
+set -eEuo pipefail
+
+# start a new log with every run of this script
+rm -f $LOOP_OUTPUT_LOG
+# make sure third_party/libwebrtc/README.moz-ff-commit is the committed version
+# so we properly determine MOZ_LIBWEBRTC_BASE and MOZ_LIBWEBRTC_NEXT_BASE
+# in the loop below
+hg revert -C third_party/libwebrtc/README.moz-ff-commit &> /dev/null
+
+# check for a resume situation from fast-forward-libwebrtc.sh
+RESUME=""
+if [ -f $STATE_DIR/resume_state ]; then
+  RESUME=`tail -1 $STATE_DIR/resume_state`
+fi
+
+ERROR_HELP=$"
+It appears that initial vendoring verification has failed.
+- If you have never run the fast-forward process before, you may need to
+  prepare the github repository by running prep_repo.sh.
+- If you have previously run loop-ff.sh successfully, there may be a new
+  change to third_party/libwebrtc that should be extracted and added to
+  the patch stack in github.  It may be as easy as running:
+      ./mach python $SCRIPT_DIR/extract-for-git.py tip::tip
+      mv mailbox.patch $MOZ_LIBWEBRTC_SRC
+      (cd $MOZ_LIBWEBRTC_SRC && \\
+       git am mailbox.patch)
+"
+# if we're not in the resume situation from fast-forward-libwebrtc.sh
+if [ "x$RESUME" = "x" ]; then
+  # start off by verifying the vendoring process to make sure no changes have
+  # been added to elm to fix bugs.
+  echo_log "Verifying vendoring..."
+  bash $SCRIPT_DIR/verify_vendoring.sh
+  echo_log "Done verifying vendoring."
+fi
+ERROR_HELP=""
+
+for (( ; ; )); do
+
+find_base_commit
+find_next_commit
+
+if [ $MOZ_LIBWEBRTC_BASE == $MOZ_LIBWEBRTC_NEXT_BASE ]; then
+  echo_log "Processing complete, already at upstream $MOZ_LIBWEBRTC_BASE"
+  exit
+fi
+
+echo_log "==================="
+
+COMMITS_REMAINING=`cd $MOZ_LIBWEBRTC_SRC ; \
+   git log --oneline $MOZ_LIBWEBRTC_BASE..$MOZ_TARGET_UPSTREAM_BRANCH_HEAD \
+   | wc -l | tr -d " "`
+echo_log "Commits remaining: $COMMITS_REMAINING"
+
+ERROR_HELP=$"Some portion of the detection and/or fixing of upstream revert commits
+has failed.  Please fix the state of the git hub repo at: $MOZ_LIBWEBRTC_SRC.
+When fixed, please resume this script with the following command:
+    SKIP_NEXT_REVERT_CHK=1 bash $SCRIPT_DIR/loop-ff.sh
+"
+if [ "x$SKIP_NEXT_REVERT_CHK" == "x0" ]; then
+  echo_log "Check for upcoming revert commit"
+  AUTO_FIX_REVERT_AS_NOOP=1 bash $SCRIPT_DIR/detect_upstream_revert.sh \
+      2>&1| tee -a $LOOP_OUTPUT_LOG
+fi
+SKIP_NEXT_REVERT_CHK="0"
+ERROR_HELP=""
+
+echo_log "Looking for $STATE_DIR/$MOZ_LIBWEBRTC_NEXT_BASE.no-op-cherry-pick-msg"
+if [ -f $STATE_DIR/$MOZ_LIBWEBRTC_NEXT_BASE.no-op-cherry-pick-msg ]; then
+  echo_log "Detected special commit msg, setting HANDLE_NOOP_COMMIT=1"
+  HANDLE_NOOP_COMMIT="1"
+fi
+
+echo_log "Moving from moz-libwebrtc commit $MOZ_LIBWEBRTC_BASE to $MOZ_LIBWEBRTC_NEXT_BASE"
+bash $SCRIPT_DIR/fast-forward-libwebrtc.sh 2>&1| tee -a $LOOP_OUTPUT_LOG
+
+MOZ_CHANGED=`hg diff -c tip --stat \
+   | egrep -ve "README.moz-ff-commit|README.mozilla|files changed," \
+   | wc -l | tr -d " " || true`
+GIT_CHANGED=`./mach python $SCRIPT_DIR/filter_git_changes.py \
+   --repo-path $MOZ_LIBWEBRTC_SRC --commit-sha $MOZ_LIBWEBRTC_NEXT_BASE \
+   | wc -l | tr -d " "`
+FILE_CNT_MISMATCH_MSG=$"
+The number of files changed in the upstream commit ($GIT_CHANGED) does
+not match the number of files changed in the local Mozilla repo
+commit ($MOZ_CHANGED).  This may indicate a mismatch between the vendoring
+script and this script, or it could be a true error in the import
+processing.  Once the issue has been resolved, the following steps
+remain for this commit:
+  # generate moz.build files (may not be necessary)
+  ./mach python python/mozbuild/mozbuild/gn_processor.py \\
+      $SCRIPT_DIR/gn-configs/webrtc.json
+  # commit the updated moz.build files with the appropriate commit msg
+  bash $SCRIPT_DIR/commit-build-file-changes.sh
+  # do a (hopefully) quick test build
+  ./mach build
+"
+echo_log "Verify number of files changed MOZ($MOZ_CHANGED) GIT($GIT_CHANGED)"
+if [ "x$HANDLE_NOOP_COMMIT" == "x1" ]; then
+  echo_log "NO-OP commit detected, we expect file changed counts to differ"
+elif [ $MOZ_CHANGED -ne $GIT_CHANGED ]; then
+  echo_log "MOZ_CHANGED $MOZ_CHANGED should equal GIT_CHANGED $GIT_CHANGED"
+  echo "$FILE_CNT_MISMATCH_MSG"
+  exit 1
+fi
+HANDLE_NOOP_COMMIT=""
+
+# save the current patch stack in case we need to reconstitute it later
+./mach python $SCRIPT_DIR/save_patch_stack.py \
+    --repo-path $MOZ_LIBWEBRTC_SRC \
+    --branch $MOZ_LIBWEBRTC_BRANCH \
+    --patch-path "third_party/libwebrtc/moz-patch-stack" \
+    --state-path $STATE_DIR \
+    --target-branch-head $MOZ_TARGET_UPSTREAM_BRANCH_HEAD \
+    2>&1| tee -a $LOOP_OUTPUT_LOG
+
+MODIFIED_BUILD_RELATED_FILE_CNT=`hg diff -c tip --stat \
+    --include 'third_party/libwebrtc/**BUILD.gn' \
+    --include 'third_party/libwebrtc/webrtc.gni' \
+    | grep -v "files changed" \
+    | wc -l | tr -d " " || true`
+ERROR_HELP=$"
+Generating build files has failed.  This likely means changes to one or more
+BUILD.gn files are required.  Commit those changes following the instructions
+in https://wiki.mozilla.org/Media/WebRTC/libwebrtc_Update_Process#Operational_notes
+Then complete these steps:
+  # generate moz.build files (may not be necessary)
+  ./mach python python/mozbuild/mozbuild/gn_processor.py \\
+      $SCRIPT_DIR/gn-configs/webrtc.json
+  # commit the updated moz.build files with the appropriate commit msg
+  bash $SCRIPT_DIR/commit-build-file-changes.sh
+  # do a (hopefully) quick test build
+  ./mach build
+After a successful build, you may resume this script.
+"
+echo_log "Modified BUILD.gn (or webrtc.gni) files: $MODIFIED_BUILD_RELATED_FILE_CNT"
+if [ "x$MODIFIED_BUILD_RELATED_FILE_CNT" != "x0" ]; then
+  echo_log "Regenerate build files"
+  ./mach python python/mozbuild/mozbuild/gn_processor.py \
+      $SCRIPT_DIR/gn-configs/webrtc.json 2>&1| tee -a $LOOP_OUTPUT_LOG
+
+  MOZ_BUILD_CHANGE_CNT=`hg status third_party/libwebrtc \
+      --include 'third_party/libwebrtc/**moz.build' | wc -l | tr -d " "`
+  if [ "x$MOZ_BUILD_CHANGE_CNT" != "x0" ]; then
+    echo_log "Detected modified moz.build files, commiting"
+  fi
+
+  bash $SCRIPT_DIR/commit-build-file-changes.sh 2>&1| tee -a $LOOP_OUTPUT_LOG
+fi
+ERROR_HELP=""
+
+ERROR_HELP=$"
+The test build has failed.  Most likely this is due to an upstream api change that
+must be reflected in Mozilla code outside of the third_party/libwebrtc directory.
+"
+echo_log "Test build"
+./mach build 2>&1| tee -a $LOOP_OUTPUT_LOG
+ERROR_HELP=""
+
+if [ ! "x$MOZ_STOP_AFTER_COMMIT" = "x" ]; then
+if [ $MOZ_LIBWEBRTC_NEXT_BASE = $MOZ_STOP_AFTER_COMMIT ]; then
+  break
+fi
+fi
+
+if [ ! "x$MOZ_ADVANCE_ONE_COMMIT" = "x" ]; then
+  echo_log "Done advancing one commit."
+  exit
+fi
+
+done
+
+echo_log "Completed fast-foward to $MOZ_STOP_AFTER_COMMIT"
diff --git a/dom/media/webrtc/third_party_build/make_upstream_revert_noop.sh b/dom/media/webrtc/third_party_build/make_upstream_revert_noop.sh
new file mode 100755
index 0000000000..9f5fdd7b82
--- /dev/null
+++ b/dom/media/webrtc/third_party_build/make_upstream_revert_noop.sh
@@ -0,0 +1,101 @@
+#!/bin/bash
+
+# This script takes the current base sha, the next base sha, and the sha
+# of the commit that reverts the next base as determined by
+# detect_upstream_revert.sh and "inserts" two commits at the bottom of the
+# moz_libwebrtc GitHub patch stack.  The two commits are exact copies of
+# the upcoming commit and its corresponding revert commit, with commit
+# messages indicating they are temporary commits.  Additionally, 2 files
+# are written that act as markers for the fast-forward script and contain
+# supplemental commit message text.
+#
+# When the fast-forward script runs, it will rebase onto the next base
+# sha.  Since we have a corresponding, identical temp commit at the bottom
+# of our patch stack, the temp commit will be absorbed as unnecessary.
+# Since the patch stack now has the temp revert commit at the bottom, this
+# results in a “no-op” commit.  The marker file indicates that specially
+# handling should occur in the fast-forward-libwebrtc.sh and loop-ff.sh
+# scripts.  This special handling includes adding the supplemental commit
+# text that explains why the commit is a no-op (or empty) commit and
+# skipping the verification of the number of files changed between our
+# mercurial repository and the GitHub repository.
+
+function show_error_msg()
+{
+  echo "*** ERROR *** $? line $1 $0 did not complete successfully!"
+  echo "$ERROR_HELP"
+}
+ERROR_HELP=""
+
+# Print an Error message if `set -eE` causes the script to exit due to a failed command
+trap 'show_error_msg $LINENO' ERR
+
+source dom/media/webrtc/third_party_build/use_config_env.sh
+
+# If DEBUG_GEN is set all commands should be printed as they are executed
+if [ ! "x$DEBUG_GEN" = "x" ]; then
+  set -x
+fi
+
+if [ "x$MOZ_LIBWEBRTC_SRC" = "x" ]; then
+  echo "MOZ_LIBWEBRTC_SRC is not defined, see README.md"
+  exit
+fi
+
+if [ -d $MOZ_LIBWEBRTC_SRC ]; then
+  echo "MOZ_LIBWEBRTC_SRC is $MOZ_LIBWEBRTC_SRC"
+else
+  echo "Path $MOZ_LIBWEBRTC_SRC is not found, see README.md"
+  exit
+fi
+
+if [ "x$MOZ_LIBWEBRTC_BRANCH" = "x" ]; then
+  echo "MOZ_LIBWEBRTC_BRANCH is not defined, see README.md"
+  exit
+fi
+
+# After this point:
+# * eE: All commands should succeed.
+# * u: All variables should be defined before use.
+# * o pipefail: All stages of all pipes should succeed.
+set -eEuo pipefail
+
+find_base_commit
+find_next_commit
+echo "MOZ_LIBWEBRTC_BASE: $MOZ_LIBWEBRTC_BASE"
+echo "MOZ_LIBWEBRTC_NEXT_BASE: $MOZ_LIBWEBRTC_NEXT_BASE"
+echo "MOZ_LIBWEBRTC_REVERT_SHA: $MOZ_LIBWEBRTC_REVERT_SHA"
+
+# These files serve dual purposes:
+# 1) They serve as marker/indicator files to loop-ff.sh to
+#    know to process the commit differently, accounting for
+#    the no-op nature of the commit and it's corresponding
+#    revert commit.
+# 2) The contain supplemental commit message text to explain
+#    why the commits are essentially empty.
+# They are written first on the off chance that the rebase
+# operation below fails and requires manual intervention,
+# thus avoiding the operator of these scripts to remember to
+# generate these two files.
+echo $"Essentially a no-op since we're going to see this change
+reverted when we vendor in $MOZ_LIBWEBRTC_REVERT_SHA." \
+> $STATE_DIR/$MOZ_LIBWEBRTC_NEXT_BASE.no-op-cherry-pick-msg
+
+echo "We already cherry-picked this when we vendored $MOZ_LIBWEBRTC_NEXT_BASE." \
+> $STATE_DIR/$MOZ_LIBWEBRTC_REVERT_SHA.no-op-cherry-pick-msg
+
+cd $MOZ_LIBWEBRTC_SRC
+rm -f $TMP_DIR/*.patch $TMP_DIR/*.patch.bak
+git checkout -b moz-cherry-pick $MOZ_LIBWEBRTC_BASE
+git format-patch -o $TMP_DIR -k --start-number 1 \
+    $MOZ_LIBWEBRTC_NEXT_BASE^..$MOZ_LIBWEBRTC_NEXT_BASE
+git format-patch -o $TMP_DIR -k --start-number 2 \
+    $MOZ_LIBWEBRTC_REVERT_SHA^..$MOZ_LIBWEBRTC_REVERT_SHA
+sed -i.bak -e "/^Subject: / s/$/ ($MOZ_LIBWEBRTC_NEXT_BASE)/" $TMP_DIR/0001*.patch
+sed -i.bak -e "/^Subject: / s/$/ ($MOZ_LIBWEBRTC_REVERT_SHA)/" $TMP_DIR/0002*.patch
+sed -i.bak -e 's/^Subject: /Subject: (tmp-cherry-pick) /' $TMP_DIR/*.patch
+git am $TMP_DIR/*.patch
+git checkout $MOZ_LIBWEBRTC_BRANCH
+git rebase moz-cherry-pick
+git branch -d moz-cherry-pick
+
diff --git a/dom/media/webrtc/third_party_build/pre-warmed-milestone.cache b/dom/media/webrtc/third_party_build/pre-warmed-milestone.cache
new file mode 100644
index 0000000000..826268db47
--- /dev/null
+++ b/dom/media/webrtc/third_party_build/pre-warmed-milestone.cache
@@ -0,0 +1 @@
+{"109": "5414", "108": "5359", "107": "5304", "106": "5249", "105": "5195"}
diff --git a/dom/media/webrtc/third_party_build/prep_repo.sh b/dom/media/webrtc/third_party_build/prep_repo.sh
new file mode 100644
index 0000000000..9f22f63253
--- /dev/null
+++ b/dom/media/webrtc/third_party_build/prep_repo.sh
@@ -0,0 +1,93 @@
+#!/bin/bash
+
+function show_error_msg()
+{
+  echo "*** ERROR *** $? line $1 $0 did not complete successfully!"
+  echo "$ERROR_HELP"
+}
+ERROR_HELP=""
+
+# Print an Error message if `set -eE` causes the script to exit due to a failed command
+trap 'show_error_msg $LINENO' ERR
+
+source dom/media/webrtc/third_party_build/use_config_env.sh
+
+echo "MOZ_LIBWEBRTC_SRC: $MOZ_LIBWEBRTC_SRC"
+echo "MOZ_LIBWEBRTC_BRANCH: $MOZ_LIBWEBRTC_BRANCH"
+echo "MOZ_FASTFORWARD_BUG: $MOZ_FASTFORWARD_BUG"
+
+# After this point:
+# * eE: All commands should succeed.
+# * u: All variables should be defined before use.
+# * o pipefail: All stages of all pipes should succeed.
+set -eEuo pipefail
+
+# wipe resume_state for new run
+rm -f $STATE_DIR/resume_state
+
+# If there is no cache file for the branch-head lookups done in
+# update_default_config.sh, go ahead and copy our small pre-warmed
+# version.
+if [ ! -f $STATE_DIR/milestone.cache ]; then
+  cp $SCRIPT_DIR/pre-warmed-milestone.cache $STATE_DIR/milestone.cache
+fi
+
+# fetch the github repro
+./mach python $SCRIPT_DIR/fetch_github_repo.py \
+    --repo-path $MOZ_LIBWEBRTC_SRC \
+    --state-path $STATE_DIR
+
+CURRENT_DIR=`pwd`
+cd $MOZ_LIBWEBRTC_SRC
+
+# clear any possible previous patches
+rm -f *.patch
+
+# create a new work branch and "export" a new patch stack to rebase
+# find the common commit between our upstream release branch and trunk
+CHERRY_PICK_BASE=`git merge-base branch-heads/$MOZ_PRIOR_UPSTREAM_BRANCH_HEAD_NUM master`
+echo "common commit: $CHERRY_PICK_BASE"
+
+# create a new branch at the common commit and checkout the new branch
+ERROR_HELP=$"
+Unable to create branch '$MOZ_LIBWEBRTC_BRANCH'.  This probably means
+that prep_repo.sh is being called on a repo that already has a patch
+stack in progress.  If you're sure you want to do this, the following
+commands will allow the process to continue:
+  ( cd $MOZ_LIBWEBRTC_SRC && \\
+    git checkout $MOZ_LIBWEBRTC_BRANCH && \\
+    git checkout -b $MOZ_LIBWEBRTC_BRANCH-old && \\
+    git branch -D $MOZ_LIBWEBRTC_BRANCH ) && \\
+  bash $0
+"
+git branch $MOZ_LIBWEBRTC_BRANCH $CHERRY_PICK_BASE
+ERROR_HELP=""
+git checkout $MOZ_LIBWEBRTC_BRANCH
+
+# make sure we're starting with a clean tmp directory
+rm -f $TMP_DIR/*.patch $TMP_DIR/*.patch.bak
+
+# grab the patches for all the commits in chrome's release branch for libwebrtc
+git format-patch -o $TMP_DIR -k $CHERRY_PICK_BASE..branch-heads/$MOZ_PRIOR_UPSTREAM_BRANCH_HEAD_NUM
+# tweak the release branch commit summaries to show they were cherry picked
+sed -i.bak -e "/^Subject: / s/^Subject: /Subject: (cherry-pick-branch-heads\/$MOZ_PRIOR_UPSTREAM_BRANCH_HEAD_NUM) /" $TMP_DIR/*.patch
+git am $TMP_DIR/*.patch # applies to branch mozpatches
+rm $TMP_DIR/*.patch $TMP_DIR/*.patch.bak
+
+# we don't use restore_patch_stack.py here because it would overwrite the patches
+# from the previous release branch we just added in the above step.
+
+# grab all the moz patches and apply
+git am $CURRENT_DIR/third_party/libwebrtc/moz-patch-stack/*.patch
+
+cd $CURRENT_DIR
+
+# cp all the no-op files to STATE_DIR
+NO_OP_FILE_COUNT=`ls third_party/libwebrtc/moz-patch-stack \
+    | grep "no-op-cherry-pick-msg" | wc -l | tr -d " " || true`
+if [ "x$NO_OP_FILE_COUNT" != "x0" ]; then
+  cp $CURRENT_DIR/third_party/libwebrtc/moz-patch-stack/*.no-op-cherry-pick-msg \
+     $STATE_DIR
+fi
+
+bash $SCRIPT_DIR/verify_vendoring.sh || true
diff --git a/dom/media/webrtc/third_party_build/push_official_branch.sh b/dom/media/webrtc/third_party_build/push_official_branch.sh
new file mode 100644
index 0000000000..e7ed17df2b
--- /dev/null
+++ b/dom/media/webrtc/third_party_build/push_official_branch.sh
@@ -0,0 +1,50 @@
+#!/bin/bash
+
+# This script is a simple helper script that creates a branch name
+# in moz-libwebrtc and pushes it to origin.  You will need permissions
+# to the mozilla fork of libwebrtc in order to complete this operation.
+# The repo is: https://github.com/mozilla/libwebrtc/
+#
+# Note: this should only be run after elm has been merged to mozilla-central
+
+function show_error_msg()
+{
+  echo "*** ERROR *** $? line $1 $0 did not complete successfully!"
+  echo "$ERROR_HELP"
+}
+ERROR_HELP=""
+
+# Print an Error message if `set -eE` causes the script to exit due to a failed command
+trap 'show_error_msg $LINENO' ERR
+
+source dom/media/webrtc/third_party_build/use_config_env.sh
+
+# After this point:
+# * eE: All commands should succeed.
+# * o pipefail: All stages of all pipes should succeed.
+set -eEo pipefail
+
+cd $MOZ_LIBWEBRTC_SRC
+
+git fetch
+
+if git show-ref --quiet refs/remotes/origin/$MOZ_LIBWEBRTC_OFFICIAL_BRANCH; then
+  echo "Branch '$MOZ_LIBWEBRTC_OFFICIAL_BRANCH' already exists remotely. Nothing to do."
+
+  echo "Please ensure this branch information can be found on Bug $MOZ_FASTFORWARD_BUG"
+  echo "https://github.com/mozilla/libwebrtc/tree/$MOZ_LIBWEBRTC_OFFICIAL_BRANCH"
+  exit 0
+fi
+
+if git show-ref --quiet refs/heads/$MOZ_LIBWEBRTC_OFFICIAL_BRANCH; then
+  echo "Branch '$MOZ_LIBWEBRTC_OFFICIAL_BRANCH' already exists locally. No need to create it."
+else
+  echo "Creating branch '$MOZ_LIBWEBRTC_OFFICIAL_BRANCH'"
+  git branch $MOZ_LIBWEBRTC_OFFICIAL_BRANCH
+fi
+
+echo "Pushing the branch to https://github.com/mozilla/libwebrtc"
+git push origin $MOZ_LIBWEBRTC_OFFICIAL_BRANCH
+
+echo "Please add this new branch information to Bug $MOZ_FASTFORWARD_BUG"
+echo "https://github.com/mozilla/libwebrtc/tree/$MOZ_LIBWEBRTC_OFFICIAL_BRANCH"
diff --git a/dom/media/webrtc/third_party_build/restore_elm_arcconfig.py b/dom/media/webrtc/third_party_build/restore_elm_arcconfig.py
new file mode 100644
index 0000000000..00c0bd7309
--- /dev/null
+++ b/dom/media/webrtc/third_party_build/restore_elm_arcconfig.py
@@ -0,0 +1,27 @@
+#!/bin/env python
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+
+from subprocess import run
+
+# This script sets the Arcanist configuration for the elm repo. This script
+# should be run after each repository reset.
+#
+# Usage: from the root of the repo `./mach python dom/media/webrtc/third_party_build/restore_elm_arcconfig.py`
+#
+
+ret = run(
+    [
+        "hg",
+        "import",
+        "-m",
+        "Bug 1729988 - FLOAT - REPO-elm - update .arcconfig repo callsign r=bgrins",
+        "dom/media/webrtc/third_party_build/elm_arcconfig.patch",
+    ]
+).returncode
+if ret != 0:
+    raise Exception(f"Failed to add FLOATing arcconfig patch for ELM: { ret }")
+else:
+    print("ELM .arcconfig restored. Please push this change to ELM")
diff --git a/dom/media/webrtc/third_party_build/restore_patch_stack.py b/dom/media/webrtc/third_party_build/restore_patch_stack.py
new file mode 100644
index 0000000000..6db3a64192
--- /dev/null
+++ b/dom/media/webrtc/third_party_build/restore_patch_stack.py
@@ -0,0 +1,107 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+import argparse
+import os
+import re
+import shutil
+
+from fetch_github_repo import fetch_repo
+from run_operations import run_git, run_shell
+
+# This script restores the mozilla patch stack and no-op commit tracking
+# files.  In the case of repo corruption or a mistake made during
+# various rebase conflict resolution operations, the patch-stack can be
+# restored rather than requiring the user to restart the fast-forward
+# process from the beginning.
+
+
+def get_last_line(file_path):
+    # technique from https://stackoverflow.com/questions/46258499/how-to-read-the-last-line-of-a-file-in-python
+    with open(file_path, "rb") as f:
+        try:  # catch OSError in case of a one line file
+            f.seek(-2, os.SEEK_END)
+            while f.read(1) != b"\n":
+                f.seek(-2, os.SEEK_CUR)
+        except OSError:
+            f.seek(0)
+        return f.readline().decode().strip()
+
+
+def restore_patch_stack(
+    github_path, github_branch, patch_directory, state_directory, tar_name
+):
+    # first, refetch the repo (hopefully utilizing the tarfile for speed) so
+    # the patches apply cleanly
+    fetch_repo(github_path, True, os.path.join(state_directory, tar_name))
+
+    # remove any stale no-op-cherry-pick-msg files in state_directory
+    run_shell("rm {}/*.no-op-cherry-pick-msg || true".format(state_directory))
+
+    # lookup latest vendored commit from third_party/libwebrtc/README.moz-ff-commit
+    file = os.path.abspath("third_party/libwebrtc/README.moz-ff-commit")
+    last_vendored_commit = get_last_line(file)
+
+    # checkout the previous vendored commit with proper branch name
+    cmd = "git checkout -b {} {}".format(github_branch, last_vendored_commit)
+    run_git(cmd, github_path)
+
+    # restore the patches to moz-libwebrtc repo, use run_shell instead of
+    # run_hg to allow filepath wildcard
+    print("Restoring patch stack")
+    run_shell("cd {} && git am {}/*.patch".format(github_path, patch_directory))
+
+    # it is also helpful to restore the no-op-cherry-pick-msg files to
+    # the state directory so that if we're restoring a patch-stack we
+    # also restore the possibly consumed no-op tracking files.
+    no_op_files = [
+        path
+        for path in os.listdir(patch_directory)
+        if re.findall(".*no-op-cherry-pick-msg$", path)
+    ]
+    for file in no_op_files:
+        shutil.copy(os.path.join(patch_directory, file), state_directory)
+
+
+if __name__ == "__main__":
+    default_patch_dir = "third_party/libwebrtc/moz-patch-stack"
+    default_state_dir = ".moz-fast-forward"
+    default_tar_name = "moz-libwebrtc.tar.gz"
+
+    parser = argparse.ArgumentParser(
+        description="Restore moz-libwebrtc github patch stack"
+    )
+    parser.add_argument(
+        "--repo-path",
+        required=True,
+        help="path to libwebrtc repo",
+    )
+    parser.add_argument(
+        "--branch",
+        default="mozpatches",
+        help="moz-libwebrtc branch (defaults to mozpatches)",
+    )
+    parser.add_argument(
+        "--patch-path",
+        default=default_patch_dir,
+        help="path to save patches (defaults to {})".format(default_patch_dir),
+    )
+    parser.add_argument(
+        "--tar-name",
+        default=default_tar_name,
+        help="name of tar file (defaults to {})".format(default_tar_name),
+    )
+    parser.add_argument(
+        "--state-path",
+        default=default_state_dir,
+        help="path to state directory (defaults to {})".format(default_state_dir),
+    )
+    args = parser.parse_args()
+
+    restore_patch_stack(
+        args.repo_path,
+        args.branch,
+        os.path.abspath(args.patch_path),
+        args.state_path,
+        args.tar_name,
+    )
diff --git a/dom/media/webrtc/third_party_build/run_operations.py b/dom/media/webrtc/third_party_build/run_operations.py
new file mode 100644
index 0000000000..794ea268d8
--- /dev/null
+++ b/dom/media/webrtc/third_party_build/run_operations.py
@@ -0,0 +1,78 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+import os
+import subprocess
+import sys
+
+# This is a collection of helper functions that use the subprocess.run
+# command to execute commands.  In the future, if we have cases where
+# we find common python functionality in utilizing the data returned
+# from these functions, that functionality can live here for easy reuse
+# between other python scripts in dom/media/webrtc/third_party_build.
+
+
+# must run 'hg' with HGPLAIN=1 to ensure aliases don't interfere with
+# command output.
+env = os.environ.copy()
+env["HGPLAIN"] = "1"
+
+
+def run_hg(cmd):
+    cmd_list = cmd.split(" ")
+    res = subprocess.run(
+        cmd_list,
+        capture_output=True,
+        text=True,
+        env=env,
+    )
+    if res.returncode != 0:
+        print(
+            "Hit return code {} running '{}'. Aborting.".format(res.returncode, cmd),
+            file=sys.stderr,
+        )
+        print(res.stderr)
+        sys.exit(1)
+    stdout = res.stdout.strip()
+    return [] if len(stdout) == 0 else stdout.split("\n")
+
+
+def run_git(cmd, working_dir):
+    cmd_list = cmd.split(" ")
+    res = subprocess.run(
+        cmd_list,
+        capture_output=True,
+        text=True,
+        cwd=working_dir,
+    )
+    if res.returncode != 0:
+        print(
+            "Hit return code {} running '{}'. Aborting.".format(res.returncode, cmd),
+            file=sys.stderr,
+        )
+        print(res.stderr)
+        sys.exit(1)
+    stdout = res.stdout.strip()
+    return [] if len(stdout) == 0 else stdout.split("\n")
+
+
+def run_shell(cmd, capture_output=True):
+    res = subprocess.run(
+        cmd,
+        shell=True,
+        capture_output=capture_output,
+        text=True,
+    )
+    if res.returncode != 0:
+        print(
+            "Hit return code {} running '{}'. Aborting.".format(res.returncode, cmd),
+            file=sys.stderr,
+        )
+        print(res.stderr)
+        sys.exit(1)
+    output_lines = []
+    if capture_output:
+        stdout = res.stdout.strip()
+        output_lines = [] if len(stdout) == 0 else stdout.split("\n")
+
+    return output_lines
diff --git a/dom/media/webrtc/third_party_build/save_patch_stack.py b/dom/media/webrtc/third_party_build/save_patch_stack.py
new file mode 100644
index 0000000000..11c007109c
--- /dev/null
+++ b/dom/media/webrtc/third_party_build/save_patch_stack.py
@@ -0,0 +1,142 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+import argparse
+import os
+import re
+import shutil
+
+from run_operations import run_git, run_hg, run_shell
+
+# This script saves the mozilla patch stack and no-op commit tracking
+# files.  This makes our fast-forward process much more resilient by
+# saving the intermediate state after each upstream commit is processed.
+
+
+def save_patch_stack(
+    github_path,
+    github_branch,
+    patch_directory,
+    state_directory,
+    target_branch_head,
+    bug_number,
+):
+    # remove the current patch files
+    files_to_remove = os.listdir(patch_directory)
+    for file in files_to_remove:
+        os.remove(os.path.join(patch_directory, file))
+
+    # find the base of the patch stack
+    cmd = "git merge-base {} {}".format(github_branch, target_branch_head)
+    stdout_lines = run_git(cmd, github_path)
+    merge_base = stdout_lines[0]
+
+    # grab patch stack
+    cmd = "git format-patch --keep-subject --output-directory {} {}..{}".format(
+        patch_directory, merge_base, github_branch
+    )
+    run_git(cmd, github_path)
+
+    # remove the commit summary from the file name
+    patches_to_rename = os.listdir(patch_directory)
+    for file in patches_to_rename:
+        shortened_name = re.sub("^(\d\d\d\d)-.*\.patch", "\\1.patch", file)
+        os.rename(
+            os.path.join(patch_directory, file),
+            os.path.join(patch_directory, shortened_name),
+        )
+
+    # remove the unhelpful first line of the patch files that only
+    # causes diff churn.  For reasons why we can't skip creating backup
+    # files during the in-place editing, see:
+    # https://stackoverflow.com/questions/5694228/sed-in-place-flag-that-works-both-on-mac-bsd-and-linux
+    run_shell("sed -i'.bak' -e '1d' {}/*.patch".format(patch_directory))
+    run_shell("rm {}/*.patch.bak".format(patch_directory))
+
+    # it is also helpful to save the no-op-cherry-pick-msg files from
+    # the state directory so that if we're restoring a patch-stack we
+    # also restore the possibly consumed no-op tracking files.
+    no_op_files = [
+        path
+        for path in os.listdir(state_directory)
+        if re.findall(".*no-op-cherry-pick-msg$", path)
+    ]
+    for file in no_op_files:
+        shutil.copy(os.path.join(state_directory, file), patch_directory)
+
+    # get missing files (that should be marked removed)
+    cmd = "hg status --no-status --deleted {}".format(patch_directory)
+    stdout_lines = run_hg(cmd)
+    if len(stdout_lines) != 0:
+        cmd = "hg rm {}".format(" ".join(stdout_lines))
+        run_hg(cmd)
+
+    # get unknown files (that should be marked added)
+    cmd = "hg status --no-status --unknown {}".format(patch_directory)
+    stdout_lines = run_hg(cmd)
+    if len(stdout_lines) != 0:
+        cmd = "hg add {}".format(" ".join(stdout_lines))
+        run_hg(cmd)
+
+    # if any files are marked for add/remove/modify, commit them
+    cmd = "hg status --added --removed --modified {}".format(patch_directory)
+    stdout_lines = run_hg(cmd)
+    if (len(stdout_lines)) != 0:
+        print("Updating {} files in {}".format(len(stdout_lines), patch_directory))
+        if bug_number is None:
+            run_hg("hg amend")
+        else:
+            run_shell(
+                "hg commit --message 'Bug {} - updated libwebrtc patch stack'".format(
+                    bug_number
+                )
+            )
+
+
+if __name__ == "__main__":
+    default_patch_dir = "third_party/libwebrtc/moz-patch-stack"
+    default_state_dir = ".moz-fast-forward"
+
+    parser = argparse.ArgumentParser(
+        description="Save moz-libwebrtc github patch stack"
+    )
+    parser.add_argument(
+        "--repo-path",
+        required=True,
+        help="path to libwebrtc repo",
+    )
+    parser.add_argument(
+        "--branch",
+        default="mozpatches",
+        help="moz-libwebrtc branch (defaults to mozpatches)",
+    )
+    parser.add_argument(
+        "--patch-path",
+        default=default_patch_dir,
+        help="path to save patches (defaults to {})".format(default_patch_dir),
+    )
+    parser.add_argument(
+        "--state-path",
+        default=default_state_dir,
+        help="path to state directory (defaults to {})".format(default_state_dir),
+    )
+    parser.add_argument(
+        "--target-branch-head",
+        required=True,
+        help="target branch head for fast-forward, should match MOZ_TARGET_UPSTREAM_BRANCH_HEAD in config_env",
+    )
+    parser.add_argument(
+        "--separate-commit-bug-number",
+        type=int,
+        help="integer Bugzilla number (example: 1800920), if provided will write patch stack as separate commit",
+    )
+    args = parser.parse_args()
+
+    save_patch_stack(
+        args.repo_path,
+        args.branch,
+        os.path.abspath(args.patch_path),
+        args.state_path,
+        args.target_branch_head,
+        args.separate_commit_bug_number,
+    )
diff --git a/dom/media/webrtc/third_party_build/update_default_config.sh b/dom/media/webrtc/third_party_build/update_default_config.sh
new file mode 100644
index 0000000000..f4020f9b45
--- /dev/null
+++ b/dom/media/webrtc/third_party_build/update_default_config.sh
@@ -0,0 +1,46 @@
+#!/bin/bash
+
+function show_error_msg()
+{
+  echo "*** ERROR *** $? line $1 $0 did not complete successfully!"
+  echo "$ERROR_HELP"
+}
+ERROR_HELP=""
+
+# Print an Error message if `set -eE` causes the script to exit due to a failed command
+trap 'show_error_msg $LINENO' ERR
+
+if [ "x" = "x$NEW_BUG_NUMBER" ]; then
+  echo "NEW_BUG_NUMBER is not defined.  You should probably have a new bug"
+  echo "number defined for the next fast-forward update.  Then do:"
+  echo "  NEW_BUG_NUMBER={new-bug-number} bash $0"
+  exit
+fi
+
+source dom/media/webrtc/third_party_build/use_config_env.sh
+
+if [ "x$MOZ_NEXT_LIBWEBRTC_MILESTONE" = "x" ]; then
+  echo "MOZ_NEXT_LIBWEBRTC_MILESTONE is not defined, see README.md"
+  exit
+fi
+
+if [ "x$MOZ_NEXT_FIREFOX_REL_TARGET" = "x" ]; then
+  echo "MOZ_NEXT_FIREFOX_REL_TARGET is not defined, see README.md"
+  exit
+fi
+
+
+# After this point:
+# * eE: All commands should succeed.
+# * u: All variables should be defined before use.
+# * o pipefail: All stages of all pipes should succeed.
+set -eEuo pipefail
+
+ERROR_HELP=$"
+An error has occurred running $SCRIPT_DIR/write_default_config.py
+"
+./mach python $SCRIPT_DIR/write_default_config.py \
+  --bug-number $NEW_BUG_NUMBER \
+  --milestone $MOZ_NEXT_LIBWEBRTC_MILESTONE \
+  --release-target $MOZ_NEXT_FIREFOX_REL_TARGET \
+  > $SCRIPT_DIR/default_config_env
diff --git a/dom/media/webrtc/third_party_build/use_config_env.sh b/dom/media/webrtc/third_party_build/use_config_env.sh
new file mode 100644
index 0000000000..bd78dc7e0e
--- /dev/null
+++ b/dom/media/webrtc/third_party_build/use_config_env.sh
@@ -0,0 +1,89 @@
+#!/bin/bash
+
+# Assume that if STATE_DIR is already defined, we do not need to
+# execute this file again.
+if [ "x$STATE_DIR" != "x" ]; then
+  # no need to run script since we've already run
+  return
+fi
+
+export SCRIPT_DIR="dom/media/webrtc/third_party_build"
+# first, make sure we're running from the top of moz-central repo
+if [ ! -d $SCRIPT_DIR ]; then
+  echo "Error: unable to find directory $SCRIPT_DIR"
+  exit 1
+fi
+
+# Should we tie the location of the STATE_DIR to the path
+# in MOZ_CONFIG_PATH?  Probably.
+export STATE_DIR=`pwd`/.moz-fast-forward
+export LOG_DIR=$STATE_DIR/logs
+export TMP_DIR=$STATE_DIR/tmp
+
+if [ ! -d $STATE_DIR ]; then
+  echo "Creating missing $STATE_DIR"
+  mkdir -p $STATE_DIR
+  if [ ! -d $STATE_DIR ]; then
+    echo "error: unable to find (or create) $STATE_DIR"
+    exit 1
+  fi
+fi
+echo "Using STATE_DIR=$STATE_DIR"
+
+if [ ! -d $LOG_DIR ]; then
+  echo "Creating missing $LOG_DIR"
+  mkdir -p $LOG_DIR
+  if [ ! -d $LOG_DIR ]; then
+    echo "error: unable to find (or create) $LOG_DIR"
+    exit 1
+  fi
+fi
+echo "Using LOG_DIR=$LOG_DIR"
+
+if [ ! -d $TMP_DIR ]; then
+  echo "Creating missing $TMP_DIR"
+  mkdir -p $TMP_DIR
+  if [ ! -d $TMP_DIR ]; then
+    echo "error: unable to find (or create) $TMP_DIR"
+    exit 1
+  fi
+fi
+echo "Using TMP_DIR=$TMP_DIR"
+
+# Allow user to override default path to config_env
+if [ "x$MOZ_CONFIG_PATH" = "x" ]; then
+  MOZ_CONFIG_PATH=$STATE_DIR/config_env
+  echo "Using default MOZ_CONFIG_PATH=$MOZ_CONFIG_PATH"
+fi
+
+if [ ! -f $MOZ_CONFIG_PATH ]; then
+  echo "Creating default config file at $MOZ_CONFIG_PATH"
+  cp $SCRIPT_DIR/default_config_env $MOZ_CONFIG_PATH
+fi
+source $MOZ_CONFIG_PATH
+
+
+function find_base_commit()
+{
+  # read the last line of README.moz-ff-commit to retrieve our current base
+  # commit in moz-libwebrtc
+  MOZ_LIBWEBRTC_BASE=`tail -1 third_party/libwebrtc/README.moz-ff-commit`
+  echo "prelim MOZ_LIBWEBRTC_BASE: $MOZ_LIBWEBRTC_BASE"
+  # if we've advanced into a chrome release branch, we need to adjust the
+  # MOZ_LIBWEBRTC_BASE to the last common commit so we can now advance up
+  # the trunk commits.
+  MOZ_LIBWEBRTC_BASE=`cd $MOZ_LIBWEBRTC_SRC ; git merge-base $MOZ_LIBWEBRTC_BASE $MOZ_TARGET_UPSTREAM_BRANCH_HEAD`
+  # now make it a short hash
+  MOZ_LIBWEBRTC_BASE=`cd $MOZ_LIBWEBRTC_SRC ; git rev-parse --short $MOZ_LIBWEBRTC_BASE`
+  echo "adjusted MOZ_LIBWEBRTC_BASE: $MOZ_LIBWEBRTC_BASE"
+}
+export -f find_base_commit
+
+function find_next_commit()
+{
+  # identify the next commit above our current base commit
+  MOZ_LIBWEBRTC_NEXT_BASE=`cd $MOZ_LIBWEBRTC_SRC ; \
+  git log --oneline --ancestry-path $MOZ_LIBWEBRTC_BASE^..$MOZ_TARGET_UPSTREAM_BRANCH_HEAD \
+   | tail -2 | head -1 | awk '{print $1;}'`
+}
+export -f find_next_commit
diff --git a/dom/media/webrtc/third_party_build/vendor-libwebrtc.py b/dom/media/webrtc/third_party_build/vendor-libwebrtc.py
new file mode 100644
index 0000000000..99723849c7
--- /dev/null
+++ b/dom/media/webrtc/third_party_build/vendor-libwebrtc.py
@@ -0,0 +1,419 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+import argparse
+import datetime
+import os
+import shutil
+import stat
+import subprocess
+import sys
+import tarfile
+
+import requests
+
+THIRDPARTY_USED_IN_FIREFOX = [
+    "abseil-cpp",
+    "google_benchmark",
+    "pffft",
+    "rnnoise",
+]
+
+LIBWEBRTC_DIR = os.path.normpath("third_party/libwebrtc")
+
+
+def get_excluded_paths():
+    return [
+        ".clang-format",
+        ".git-blame-ignore-revs",
+        ".gitignore",
+        ".vpython",
+        "CODE_OF_CONDUCT.md",
+        "ENG_REVIEW_OWNERS",
+        "PRESUBMIT.py",
+        "README.chromium",
+        "WATCHLISTS",
+        "codereview.settings",
+        "license_template.txt",
+        "native-api.md",
+        "presubmit_test.py",
+        "presubmit_test_mocks.py",
+        "pylintrc",
+        # Only the camera code under sdk/android/api/org/webrtc is used, so
+        # we remove sdk/android and add back the specific files we want.
+        "sdk/android",
+    ]
+
+
+# Paths in this list are included even if their parent directory is
+# excluded in get_excluded_paths()
+def get_included_path_overrides():
+    return [
+        "sdk/android/src/java/org/webrtc/NativeLibrary.java",
+        "sdk/android/src/java/org/webrtc/FramerateBitrateAdjuster.java",
+        "sdk/android/src/java/org/webrtc/MediaCodecVideoDecoderFactory.java",
+        "sdk/android/src/java/org/webrtc/BitrateAdjuster.java",
+        "sdk/android/src/java/org/webrtc/MediaCodecWrapperFactory.java",
+        "sdk/android/src/java/org/webrtc/WebRtcClassLoader.java",
+        "sdk/android/src/java/org/webrtc/audio/WebRtcAudioRecord.java",
+        "sdk/android/src/java/org/webrtc/audio/WebRtcAudioTrack.java",
+        "sdk/android/src/java/org/webrtc/audio/WebRtcAudioManager.java",
+        "sdk/android/src/java/org/webrtc/audio/LowLatencyAudioBufferManager.java",
+        "sdk/android/src/java/org/webrtc/audio/WebRtcAudioUtils.java",
+        "sdk/android/src/java/org/webrtc/audio/WebRtcAudioEffects.java",
+        "sdk/android/src/java/org/webrtc/audio/VolumeLogger.java",
+        "sdk/android/src/java/org/webrtc/NativeCapturerObserver.java",
+        "sdk/android/src/java/org/webrtc/MediaCodecWrapper.java",
+        "sdk/android/src/java/org/webrtc/CalledByNative.java",
+        "sdk/android/src/java/org/webrtc/Histogram.java",
+        "sdk/android/src/java/org/webrtc/EglBase10Impl.java",
+        "sdk/android/src/java/org/webrtc/EglBase14Impl.java",
+        "sdk/android/src/java/org/webrtc/MediaCodecWrapperFactoryImpl.java",
+        "sdk/android/src/java/org/webrtc/AndroidVideoDecoder.java",
+        "sdk/android/src/java/org/webrtc/BaseBitrateAdjuster.java",
+        "sdk/android/src/java/org/webrtc/HardwareVideoEncoder.java",
+        "sdk/android/src/java/org/webrtc/VideoCodecMimeType.java",
+        "sdk/android/src/java/org/webrtc/NativeAndroidVideoTrackSource.java",
+        "sdk/android/src/java/org/webrtc/VideoDecoderWrapper.java",
+        "sdk/android/src/java/org/webrtc/JNILogging.java",
+        "sdk/android/src/java/org/webrtc/CameraCapturer.java",
+        "sdk/android/src/java/org/webrtc/CameraSession.java",
+        "sdk/android/src/java/org/webrtc/H264Utils.java",
+        "sdk/android/src/java/org/webrtc/Empty.java",
+        "sdk/android/src/java/org/webrtc/DynamicBitrateAdjuster.java",
+        "sdk/android/src/java/org/webrtc/Camera1Session.java",
+        "sdk/android/src/java/org/webrtc/JniCommon.java",
+        "sdk/android/src/java/org/webrtc/NV12Buffer.java",
+        "sdk/android/src/java/org/webrtc/WrappedNativeI420Buffer.java",
+        "sdk/android/src/java/org/webrtc/GlGenericDrawer.java",
+        "sdk/android/src/java/org/webrtc/RefCountDelegate.java",
+        "sdk/android/src/java/org/webrtc/Camera2Session.java",
+        "sdk/android/src/java/org/webrtc/MediaCodecUtils.java",
+        "sdk/android/src/java/org/webrtc/CalledByNativeUnchecked.java",
+        "sdk/android/src/java/org/webrtc/VideoEncoderWrapper.java",
+        "sdk/android/src/java/org/webrtc/NV21Buffer.java",
+        "sdk/android/api/org/webrtc/RendererCommon.java",
+        "sdk/android/api/org/webrtc/YuvHelper.java",
+        "sdk/android/api/org/webrtc/LibvpxVp9Encoder.java",
+        "sdk/android/api/org/webrtc/Metrics.java",
+        "sdk/android/api/org/webrtc/CryptoOptions.java",
+        "sdk/android/api/org/webrtc/MediaConstraints.java",
+        "sdk/android/api/org/webrtc/YuvConverter.java",
+        "sdk/android/api/org/webrtc/JavaI420Buffer.java",
+        "sdk/android/api/org/webrtc/VideoDecoder.java",
+        "sdk/android/api/org/webrtc/WrappedNativeVideoDecoder.java",
+        "sdk/android/api/org/webrtc/Camera2Enumerator.java",
+        "sdk/android/api/org/webrtc/SurfaceTextureHelper.java",
+        "sdk/android/api/org/webrtc/EglBase10.java",
+        "sdk/android/api/org/webrtc/DataChannel.java",
+        "sdk/android/api/org/webrtc/audio/JavaAudioDeviceModule.java",
+        "sdk/android/api/org/webrtc/audio/AudioDeviceModule.java",
+        "sdk/android/api/org/webrtc/audio/LegacyAudioDeviceModule.java",
+        "sdk/android/api/org/webrtc/SessionDescription.java",
+        "sdk/android/api/org/webrtc/GlUtil.java",
+        "sdk/android/api/org/webrtc/VideoSource.java",
+        "sdk/android/api/org/webrtc/AudioTrack.java",
+        "sdk/android/api/org/webrtc/EglRenderer.java",
+        "sdk/android/api/org/webrtc/VideoEncoder.java",
+        "sdk/android/api/org/webrtc/VideoCapturer.java",
+        "sdk/android/api/org/webrtc/SoftwareVideoDecoderFactory.java",
+        "sdk/android/api/org/webrtc/AudioSource.java",
+        "sdk/android/api/org/webrtc/GlRectDrawer.java",
+        "sdk/android/api/org/webrtc/StatsReport.java",
+        "sdk/android/api/org/webrtc/CameraVideoCapturer.java",
+        "sdk/android/api/org/webrtc/NetEqFactoryFactory.java",
+        "sdk/android/api/org/webrtc/AudioProcessingFactory.java",
+        "sdk/android/api/org/webrtc/Camera2Capturer.java",
+        "sdk/android/api/org/webrtc/ScreenCapturerAndroid.java",
+        "sdk/android/api/org/webrtc/RefCounted.java",
+        "sdk/android/api/org/webrtc/VideoEncoderFallback.java",
+        "sdk/android/api/org/webrtc/AudioEncoderFactoryFactory.java",
+        "sdk/android/api/org/webrtc/EglBase14.java",
+        "sdk/android/api/org/webrtc/SoftwareVideoEncoderFactory.java",
+        "sdk/android/api/org/webrtc/VideoEncoderFactory.java",
+        "sdk/android/api/org/webrtc/StatsObserver.java",
+        "sdk/android/api/org/webrtc/PlatformSoftwareVideoDecoderFactory.java",
+        "sdk/android/api/org/webrtc/Camera1Capturer.java",
+        "sdk/android/api/org/webrtc/AddIceObserver.java",
+        "sdk/android/api/org/webrtc/SurfaceViewRenderer.java",
+        "sdk/android/api/org/webrtc/CameraEnumerator.java",
+        "sdk/android/api/org/webrtc/CameraEnumerationAndroid.java",
+        "sdk/android/api/org/webrtc/VideoDecoderFallback.java",
+        "sdk/android/api/org/webrtc/FileVideoCapturer.java",
+        "sdk/android/api/org/webrtc/NativeLibraryLoader.java",
+        "sdk/android/api/org/webrtc/Camera1Enumerator.java",
+        "sdk/android/api/org/webrtc/NativePeerConnectionFactory.java",
+        "sdk/android/api/org/webrtc/LibaomAv1Encoder.java",
+        "sdk/android/api/org/webrtc/BuiltinAudioEncoderFactoryFactory.java",
+        "sdk/android/api/org/webrtc/AudioDecoderFactoryFactory.java",
+        "sdk/android/api/org/webrtc/FecControllerFactoryFactoryInterface.java",
+        "sdk/android/api/org/webrtc/VideoFrameBufferType.java",
+        "sdk/android/api/org/webrtc/SdpObserver.java",
+        "sdk/android/api/org/webrtc/Predicate.java",
+        "sdk/android/api/org/webrtc/VideoFileRenderer.java",
+        "sdk/android/api/org/webrtc/WrappedNativeVideoEncoder.java",
+        "sdk/android/api/org/webrtc/LibvpxVp8Encoder.java",
+        "sdk/android/api/org/webrtc/DtmfSender.java",
+        "sdk/android/api/org/webrtc/VideoTrack.java",
+        "sdk/android/api/org/webrtc/LibvpxVp8Decoder.java",
+        "sdk/android/api/org/webrtc/GlShader.java",
+        "sdk/android/api/org/webrtc/FrameEncryptor.java",
+        "sdk/android/api/org/webrtc/EglBase.java",
+        "sdk/android/api/org/webrtc/VideoProcessor.java",
+        "sdk/android/api/org/webrtc/SSLCertificateVerifier.java",
+        "sdk/android/api/org/webrtc/VideoSink.java",
+        "sdk/android/api/org/webrtc/MediaSource.java",
+        "sdk/android/api/org/webrtc/DefaultVideoDecoderFactory.java",
+        "sdk/android/api/org/webrtc/VideoCodecInfo.java",
+        "sdk/android/api/org/webrtc/FrameDecryptor.java",
+        "sdk/android/api/org/webrtc/VideoDecoderFactory.java",
+        "sdk/android/api/org/webrtc/TextureBufferImpl.java",
+        "sdk/android/api/org/webrtc/VideoFrame.java",
+        "sdk/android/api/org/webrtc/IceCandidateErrorEvent.java",
+        "sdk/android/api/org/webrtc/CapturerObserver.java",
+        "sdk/android/api/org/webrtc/MediaStreamTrack.java",
+        "sdk/android/api/org/webrtc/GlTextureFrameBuffer.java",
+        "sdk/android/api/org/webrtc/TurnCustomizer.java",
+        "sdk/android/api/org/webrtc/TimestampAligner.java",
+        "sdk/android/api/org/webrtc/BuiltinAudioDecoderFactoryFactory.java",
+        "sdk/android/api/org/webrtc/LibvpxVp9Decoder.java",
+        "sdk/android/api/org/webrtc/SurfaceEglRenderer.java",
+        "sdk/android/api/org/webrtc/HardwareVideoDecoderFactory.java",
+        "sdk/android/api/org/webrtc/VideoCodecStatus.java",
+        "sdk/android/api/org/webrtc/Dav1dDecoder.java",
+        "sdk/android/api/org/webrtc/VideoFrameDrawer.java",
+        "sdk/android/api/org/webrtc/CallSessionFileRotatingLogSink.java",
+        "sdk/android/api/org/webrtc/EncodedImage.java",
+    ]
+
+
+def make_github_url(repo, commit):
+    if not repo.endswith("/"):
+        repo += "/"
+    return repo + "archive/" + commit + ".tar.gz"
+
+
+def make_googlesource_url(target, commit):
+    if target == "libwebrtc":
+        return "https://webrtc.googlesource.com/src.git/+archive/" + commit + ".tar.gz"
+    elif target == "build":
+        return (
+            "https://chromium.googlesource.com/chromium/src/build/+archive/"
+            + commit
+            + ".tar.gz"
+        )
+    elif target == "third_party":
+        return (
+            "https://chromium.googlesource.com/chromium/src/third_party/+archive/"
+            + commit
+            + ".tar.gz"
+        )
+
+
+def fetch(target, url):
+    print("Fetching commit from {}".format(url))
+    req = requests.get(url)
+    if req.status_code == 200:
+        with open(target + ".tar.gz", "wb") as f:
+            f.write(req.content)
+    else:
+        print(
+            "Hit status code {} fetching commit. Aborting.".format(req.status_code),
+            file=sys.stderr,
+        )
+        sys.exit(1)
+    with open(os.path.join(LIBWEBRTC_DIR, "README.mozilla"), "a") as f:
+        # write the the command line used
+        f.write("# ./mach python {}\n".format(" ".join(sys.argv[0:])))
+        f.write(
+            "{} updated from commit {} on {}.\n".format(
+                target, url, datetime.datetime.utcnow().isoformat()
+            )
+        )
+
+
+def fetch_local(target, path, commit):
+    target_archive = target + ".tar.gz"
+    cp = subprocess.run(["git", "archive", "-o", target_archive, commit], cwd=path)
+    if cp.returncode != 0:
+        print(
+            "Hit return code {} fetching commit. Aborting.".format(cp.returncode),
+            file=sys.stderr,
+        )
+        sys.exit(1)
+
+    with open(os.path.join(LIBWEBRTC_DIR, "README.mozilla"), "a") as f:
+        # write the the command line used
+        f.write("# ./mach python {}\n".format(" ".join(sys.argv[0:])))
+        f.write(
+            "{} updated from {} commit {} on {}.\n".format(
+                target, path, commit, datetime.datetime.utcnow().isoformat()
+            )
+        )
+    shutil.move(os.path.join(path, target_archive), target_archive)
+
+
+def validate_tar_member(member, path):
+    def _is_within_directory(directory, target):
+        real_directory = os.path.realpath(directory)
+        real_target = os.path.realpath(target)
+        prefix = os.path.commonprefix([real_directory, real_target])
+        return prefix == real_directory
+
+    member_path = os.path.join(path, member.name)
+    if not _is_within_directory(path, member_path):
+        raise Exception("Attempted path traversal in tar file: " + member.name)
+    if member.issym():
+        link_path = os.path.join(os.path.dirname(member_path), member.linkname)
+        if not _is_within_directory(path, link_path):
+            raise Exception("Attempted link path traversal in tar file: " + member.name)
+    if member.mode & (stat.S_ISUID | stat.S_ISGID):
+        raise Exception("Attempted setuid or setgid in tar file: " + member.name)
+
+
+def safe_extract(tar, path=".", *, numeric_owner=False):
+    def _files(tar, path):
+        for member in tar:
+            validate_tar_member(member, path)
+            yield member
+
+    tar.extractall(path, members=_files(tar, path), numeric_owner=numeric_owner)
+
+
+def unpack(target):
+    target_archive = target + ".tar.gz"
+    target_path = "tmp-" + target
+    try:
+        shutil.rmtree(target_path)
+    except FileNotFoundError:
+        pass
+    with tarfile.open(target_archive) as t:
+        safe_extract(t, path=target_path)
+
+    if target == "libwebrtc":
+        # use the top level directories from the tarfile and
+        # delete those directories in LIBWEBRTC_DIR
+        libwebrtc_used_in_firefox = os.listdir(target_path)
+        for path in libwebrtc_used_in_firefox:
+            try:
+                shutil.rmtree(os.path.join(LIBWEBRTC_DIR, path))
+            except FileNotFoundError:
+                pass
+            except NotADirectoryError:
+                pass
+
+        unused_libwebrtc_in_firefox = get_excluded_paths()
+        forced_used_in_firefox = get_included_path_overrides()
+
+        # adjust target_path if GitHub packaging is involved
+        if not os.path.exists(os.path.join(target_path, libwebrtc_used_in_firefox[0])):
+            # GitHub packs everything inside a separate directory
+            target_path = os.path.join(target_path, os.listdir(target_path)[0])
+
+        # remove any entries found in unused_libwebrtc_in_firefox from the
+        # tarfile
+        for path in unused_libwebrtc_in_firefox:
+            if os.path.isdir(os.path.join(target_path, path)):
+                shutil.rmtree(os.path.join(target_path, path))
+            else:
+                os.remove(os.path.join(target_path, path))
+
+        # move remaining top level entries from the tarfile to LIBWEBRTC_DIR
+        for path in os.listdir(target_path):
+            shutil.move(
+                os.path.join(target_path, path), os.path.join(LIBWEBRTC_DIR, path)
+            )
+
+        # An easy, but inefficient way to accomplish including specific
+        # files from directories otherwise removed.  Re-extract the tar
+        # file, and only copy over the exact files requested.
+        shutil.rmtree(target_path)
+        with tarfile.open(target_archive) as t:
+            safe_extract(t, path=target_path)
+
+        # Copy the force included files.  Note: the instinctual action
+        # is to do this prior to removing the excluded paths to avoid
+        # reextracting the tar file.  However, this causes errors due to
+        # pre-existing paths when other directories are moved out of the
+        # tar file in the "move all the top level entries from the
+        # tarfile" phase above.
+        for path in forced_used_in_firefox:
+            dest_path = os.path.join(LIBWEBRTC_DIR, path)
+            dir_path = os.path.dirname(dest_path)
+            if not os.path.exists(dir_path):
+                os.makedirs(dir_path)
+            shutil.move(os.path.join(target_path, path), dest_path)
+    elif target == "build":
+        try:
+            shutil.rmtree(os.path.join(LIBWEBRTC_DIR, "build"))
+        except FileNotFoundError:
+            pass
+        os.makedirs(os.path.join(LIBWEBRTC_DIR, "build"))
+
+        if os.path.exists(os.path.join(target_path, "linux")):
+            for path in os.listdir(target_path):
+                shutil.move(
+                    os.path.join(target_path, path),
+                    os.path.join(LIBWEBRTC_DIR, "build", path),
+                )
+        else:
+            # GitHub packs everything inside a separate directory
+            target_path = os.path.join(target_path, os.listdir(target_path)[0])
+            for path in os.listdir(target_path):
+                shutil.move(
+                    os.path.join(target_path, path),
+                    os.path.join(LIBWEBRTC_DIR, "build", path),
+                )
+    elif target == "third_party":
+        try:
+            shutil.rmtree(os.path.join(LIBWEBRTC_DIR, "third_party"))
+        except FileNotFoundError:
+            pass
+        except NotADirectoryError:
+            pass
+
+        if os.path.exists(os.path.join(target_path, THIRDPARTY_USED_IN_FIREFOX[0])):
+            for path in THIRDPARTY_USED_IN_FIREFOX:
+                shutil.move(
+                    os.path.join(target_path, path),
+                    os.path.join(LIBWEBRTC_DIR, "third_party", path),
+                )
+        else:
+            # GitHub packs everything inside a separate directory
+            target_path = os.path.join(target_path, os.listdir(target_path)[0])
+            for path in THIRDPARTY_USED_IN_FIREFOX:
+                shutil.move(
+                    os.path.join(target_path, path),
+                    os.path.join(LIBWEBRTC_DIR, "third_party", path),
+                )
+
+
+def cleanup(target):
+    os.remove(target + ".tar.gz")
+    shutil.rmtree("tmp-" + target)
+
+
+if __name__ == "__main__":
+    parser = argparse.ArgumentParser(description="Update libwebrtc")
+    parser.add_argument("target", choices=("libwebrtc", "build", "third_party"))
+    group = parser.add_mutually_exclusive_group(required=True)
+    group.add_argument("--from-github", type=str)
+    group.add_argument("--from-googlesource", action="store_true", default=False)
+    group.add_argument("--from-local", type=str)
+    parser.add_argument("--commit", type=str, default="master")
+    parser.add_argument("--skip-fetch", action="store_true", default=False)
+    parser.add_argument("--skip-cleanup", action="store_true", default=False)
+    args = parser.parse_args()
+
+    os.makedirs(LIBWEBRTC_DIR, exist_ok=True)
+
+    if not args.skip_fetch:
+        if args.from_github:
+            fetch(args.target, make_github_url(args.from_github, args.commit))
+        elif args.from_googlesource:
+            fetch(args.target, make_googlesource_url(args.target, args.commit))
+        elif args.from_local:
+            fetch_local(args.target, args.from_local, args.commit)
+    unpack(args.target)
+    if not args.skip_cleanup:
+        cleanup(args.target)
diff --git a/dom/media/webrtc/third_party_build/verify_vendoring.sh b/dom/media/webrtc/third_party_build/verify_vendoring.sh
new file mode 100644
index 0000000000..3d2c161075
--- /dev/null
+++ b/dom/media/webrtc/third_party_build/verify_vendoring.sh
@@ -0,0 +1,55 @@
+#!/bin/bash
+
+function show_error_msg()
+{
+  echo "*** ERROR *** $? line $1 $0 did not complete successfully!"
+  echo "$ERROR_HELP"
+}
+ERROR_HELP=""
+
+# Print an Error message if `set -eE` causes the script to exit due to a failed command
+trap 'show_error_msg $LINENO' ERR
+
+source dom/media/webrtc/third_party_build/use_config_env.sh
+
+echo "MOZ_LIBWEBRTC_SRC: $MOZ_LIBWEBRTC_SRC"
+echo "MOZ_LIBWEBRTC_BRANCH: $MOZ_LIBWEBRTC_BRANCH"
+echo "MOZ_FASTFORWARD_BUG: $MOZ_FASTFORWARD_BUG"
+
+# After this point:
+# * eE: All commands should succeed.
+# * u: All variables should be defined before use.
+# * o pipefail: All stages of all pipes should succeed.
+set -eEuo pipefail
+
+./mach python $SCRIPT_DIR/vendor-libwebrtc.py \
+        --from-local $MOZ_LIBWEBRTC_SRC \
+        --commit $MOZ_LIBWEBRTC_BRANCH \
+        libwebrtc
+
+hg revert -q \
+   --include "third_party/libwebrtc/**moz.build" \
+   --include "third_party/libwebrtc/README.mozilla" \
+   third_party/libwebrtc
+
+FILE_CHANGE_CNT=`hg status third_party/libwebrtc | wc -l | tr -d " "`
+if [ "x$FILE_CHANGE_CNT" != "x0" ]; then
+  echo "***"
+  echo "There are changes after vendoring - running extract-for-git.py"
+  echo "is recommended.  First, find the mercurial commit after the"
+  echo "previous fast-forward landing.  The commands you want will look"
+  echo "something like:"
+  echo "  ./mach python $SCRIPT_DIR/extract-for-git.py {after-ff-commit}::{tip-of-central}"
+  echo "  mv mailbox.patch $MOZ_LIBWEBRTC_SRC"
+  echo "  (cd $MOZ_LIBWEBRTC_SRC && \\"
+  echo "   git am mailbox.patch)"
+  echo ""
+  echo "After adding the new changes from moz-central to the moz-libwebrtc"
+  echo "patch stack, you may re-run this command to verify vendoring:"
+  echo "  bash $0"
+
+  exit 1
+fi
+
+
+echo "Done - vendoring has been verified."
diff --git a/dom/media/webrtc/third_party_build/webrtc.mozbuild b/dom/media/webrtc/third_party_build/webrtc.mozbuild
new file mode 100644
index 0000000000..30169c36c2
--- /dev/null
+++ b/dom/media/webrtc/third_party_build/webrtc.mozbuild
@@ -0,0 +1,40 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+# This file mimics the defines used by any headers in libwebrtc that get
+# included in Mozilla code.
+# We currently audit these by hand. Searching for the defines upstream is a good
+# start:
+# https://source.chromium.org/search?q=usage:%23if.*def.*%5B%5E_%5D$%20AND%20path:%5C.h%20AND%20path:%5Ethird_party%2Fwebrtc&ss=chromium
+
+if CONFIG['MOZ_WEBRTC']:
+    DEFINES['HAVE_UINT64_T'] = True
+    DEFINES['WEBRTC_MOZILLA_BUILD'] = True
+    DEFINES['RTC_ENABLE_VP9'] = True
+
+    if CONFIG['OS_TARGET'] != 'WINNT':
+        DEFINES['WEBRTC_POSIX'] = True
+        DEFINES['WEBRTC_BUILD_LIBEVENT'] = True
+
+    if CONFIG['OS_TARGET'] == 'Linux':
+        DEFINES['WEBRTC_LINUX'] = True
+    elif CONFIG['OS_TARGET'] == 'Darwin':
+        DEFINES['WEBRTC_MAC'] = True
+    elif CONFIG['OS_TARGET'] == 'WINNT':
+        DEFINES['WEBRTC_WIN'] = True
+        DEFINES['RTC_ENABLE_WIN_WGC'] = False
+        DEFINES['HAVE_WINSOCK2_H'] = True
+    elif CONFIG['OS_TARGET'] in ('DragonFly', 'FreeBSD', 'NetBSD', 'OpenBSD'):
+        DEFINES['WEBRTC_BSD'] = True
+    elif CONFIG['OS_TARGET'] == 'Android':
+        DEFINES['WEBRTC_LINUX'] = True
+        DEFINES['WEBRTC_ANDROID'] = True
+
+    if CONFIG['MOZ_X11']:
+        DEFINES['WEBRTC_USE_X11'] = True
+
+    if CONFIG["MOZ_WIDGET_TOOLKIT"] == "gtk":
+        DEFINES['WEBRTC_USE_PIPEWIRE'] = True
diff --git a/dom/media/webrtc/third_party_build/write_default_config.py b/dom/media/webrtc/third_party_build/write_default_config.py
new file mode 100644
index 0000000000..204789e052
--- /dev/null
+++ b/dom/media/webrtc/third_party_build/write_default_config.py
@@ -0,0 +1,104 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+import argparse
+import sys
+from string import Template
+
+sys.path.insert(0, "./dom/media/webrtc/third_party_build")
+import lookup_branch_head
+
+text = """#!/bin/bash
+
+# Edit {path-to} to match the location of your copy of Mozilla's
+# fork of libwebrtc (at https://github.com/mozilla/libwebrtc).
+export MOZ_LIBWEBRTC_SRC=$$STATE_DIR/moz-libwebrtc
+
+# Fast-forwarding each Chromium version of libwebrtc should be done
+# under a separate bugzilla bug.  This bug number is used when crafting
+# the commit summary as each upstream commit is vendored into the
+# mercurial repository.  The bug used for the v106 fast-forward was
+# 1800920.
+export MOZ_FASTFORWARD_BUG="$bugnum"
+
+# MOZ_NEXT_LIBWEBRTC_MILESTONE and MOZ_NEXT_FIREFOX_REL_TARGET are
+# not used during fast-forward processing, but facilitate generating this
+# default config.  To generate an default config for the next update, run
+# bash dom/media/webrtc/third_party_build/update_default_config_env.sh
+export MOZ_NEXT_LIBWEBRTC_MILESTONE=$m2
+export MOZ_NEXT_FIREFOX_REL_TARGET=$t2
+
+# For Chromium release branches, see:
+# https://chromiumdash.appspot.com/branches
+
+# Chromium's v$m1 release branch was $bh1.  This is used to pre-stack
+# the previous release branch's commits onto the appropriate base commit
+# (the first common commit between trunk and the release branch).
+export MOZ_PRIOR_UPSTREAM_BRANCH_HEAD_NUM="$bh1"
+
+# New target release branch for v$m2 is branch-heads/$bh2.  This is used
+# to calculate the next upstream commit.
+export MOZ_TARGET_UPSTREAM_BRANCH_HEAD="branch-heads/$bh2"
+
+# For local development 'mozpatches' is fine for a branch name, but when
+# pushing the patch stack to github, it should be named something like
+# 'moz-mods-chr$m2-for-rel$t2'.
+export MOZ_LIBWEBRTC_BRANCH="mozpatches"
+
+# After elm has been merged to mozilla-central, the patch stack in
+# moz-libwebrtc should be pushed to github.  The script
+# push_official_branch.sh uses this branch name when pushing to the
+# public repo.
+export MOZ_LIBWEBRTC_OFFICIAL_BRANCH="moz-mods-chr$m2-for-rel$t2"
+"""
+
+
+def build_default_config_env(bug_number, milestone, target):
+    prior_branch_head = lookup_branch_head.get_branch_head(milestone)
+    if prior_branch_head is None:
+        sys.exit("error: chromium milestone '{}' is not found.".format(milestone))
+    new_branch_head = lookup_branch_head.get_branch_head(milestone + 1)
+    if new_branch_head is None:
+        sys.exit(
+            "error: next chromium milestone '{}' is not found.".format(milestone + 1)
+        )
+
+    s = Template(text)
+    return s.substitute(
+        bugnum=bug_number,
+        m1=milestone,
+        m2=milestone + 1,
+        t2=target + 1,
+        bh1=prior_branch_head,
+        bh2=new_branch_head,
+    )
+
+
+if __name__ == "__main__":
+    parser = argparse.ArgumentParser(
+        description="Updates the default_config_env file for new release/milestone"
+    )
+    parser.add_argument(
+        "--bug-number",
+        required=True,
+        type=int,
+        help="integer Bugzilla number (example: 1800920)",
+    )
+    parser.add_argument(
+        "--milestone",
+        required=True,
+        type=int,
+        help="integer chromium milestone (example: 106)",
+    )
+    parser.add_argument(
+        "--release-target",
+        required=True,
+        type=int,
+        help="integer firefox release (example: 110)",
+    )
+    args = parser.parse_args()
+
+    print(
+        build_default_config_env(args.bug_number, args.milestone, args.release_target),
+        end="",
+    )