Bug 1918268 - Vendor libwebrtc from 21508e08e7

Upstream commit: https://webrtc.googlesource.com/src/+/21508e08e7545a03c8c35a9299923279e3def319
    Fix license metadata for spl_sqrt_floor, portaudio, sigslot

    (cherry picked from commit 6ea1c96325baada0e6ba0b29456e02f403e15a1e)

    Bug: b/361140175
    Change-Id: I35e76039608fa5094c04ace5f3ad1dba868ccb85
    Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/360900
    Reviewed-by: Henrik Andreassson <henrikawebrtc.org>
    Commit-Queue: Andrew Grieve <agrievegoogle.com>
    Cr-Original-Commit-Position: refs/heads/main{#42885}
    Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/361520
    Reviewed-by: Mirko Bonadei <mbonadeiwebrtc.org>
    Reviewed-by: Harald Alvestrand <htawebrtc.org>
    Commit-Queue: Mirko Bonadei <mbonadeiwebrtc.org>
    Cr-Commit-Position: refs/branch-heads/6668{#1}
    Cr-Branched-From: 2cfedb277ae8dd2a8d8dd68aca6f95081c265671-refs/heads/main{#42810}

UltraBlame original commit: fff71dac56c57f10e67e8ea3f1ea7eaeb103f0aa

third_party/libwebrtc/README.moz-ff-commit

@@ -32217,3 +32217,6 @@ b1ffa9bd4e
 # MOZ_LIBWEBRTC_SRC=/home/mfroman/mozilla/elm/.moz-fast-forward/moz-libwebrtc MOZ_LIBWEBRTC_BRANCH=mozpatches bash dom/media/webrtc/third_party_build/fast-forward-libwebrtc.sh
 # base of lastest vendoring
 2cfedb277a
+# MOZ_LIBWEBRTC_SRC=/home/mfroman/mozilla/elm/.moz-fast-forward/moz-libwebrtc MOZ_LIBWEBRTC_BRANCH=mozpatches bash dom/media/webrtc/third_party_build/fast-forward-libwebrtc.sh
+# base of lastest vendoring
+21508e08e7

third_party/libwebrtc/README.mozilla

@@ -21502,3 +21502,5 @@ libwebrtc updated from /home/mfroman/mozilla/elm/.moz-fast-forward/moz-libwebrtc
 libwebrtc updated from /home/mfroman/mozilla/elm/.moz-fast-forward/moz-libwebrtc commit mozpatches on 2024-09-19T20:23:54.070683.
 # ./mach python dom/media/webrtc/third_party_build/vendor-libwebrtc.py --from-local /home/mfroman/mozilla/elm/.moz-fast-forward/moz-libwebrtc --commit mozpatches libwebrtc
 libwebrtc updated from /home/mfroman/mozilla/elm/.moz-fast-forward/moz-libwebrtc commit mozpatches on 2024-09-19T20:24:53.241903.
+# ./mach python dom/media/webrtc/third_party_build/vendor-libwebrtc.py --from-local /home/mfroman/mozilla/elm/.moz-fast-forward/moz-libwebrtc --commit mozpatches libwebrtc
+libwebrtc updated from /home/mfroman/mozilla/elm/.moz-fast-forward/moz-libwebrtc commit mozpatches on 2024-09-19T20:25:47.254928.

third_party/libwebrtc/common_audio/third_party/spl_sqrt_floor/README.chromium

@@ -3,7 +3,7 @@ Short Name: sql_sqrt_floor
 URL: http://www.pertinentdetail.org/sqrt
 Version: 0
 Date: 2018-03-22
-License: Custom license
+License: SPL-SQRT-FLOOR
 License File: LICENSE
 Security Critical: yes
 Shipped: yes

third_party/libwebrtc/modules/third_party/portaudio/README.chromium

@@ -3,7 +3,7 @@ Short Name: portaudio
 URL: https://github.com/PortAudio/portaudio/tree/master/src/common
 Version: 9d8563100d841300f1689b186d131347ad43a0f6
 Date: 2022-04-12
-License: Custom license
+License: MIT
 License File: LICENSE
 Security Critical: yes
 Shipped: yes

third_party/libwebrtc/rtc_base/third_party/sigslot/README.chromium

@@ -3,7 +3,7 @@ Short Name: sigslot
 URL: http://sigslot.sourceforge.net/
 Version: 0
 Date: 2018-07-09
-License: Custom license
+License: Ignorable
 License File: LICENSE
 Security Critical: yes
 Shipped: yes