RTCDTMFSender: interToneGap is not clamped to 6000 ms and is waited twice between tones - #78217

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RTCDTMFSender: interToneGap is not clamped to 6000 ms and is waited twice between tones
https://bugs.webkit.org/show_bug.cgi?id=328831
rdar://190946556

Reviewed by NOBODY (OOPS!).

This patch aligns WebKit with Gecko / Firefox.

Per the WebRTC spec [1], insertDTMF() sets [[InterToneGap]] to 6000 ms if
the given value is greater than 6000 ms, in addition to raising values
below 30 ms to 30 ms. We only applied the lower bound, so a large
interToneGap was used as is. Clamp it to [30, 6000] with std::clamp, and
use std::clamp for duration as well so both lines match.

The spec also queues the next playout task duration + interToneGap after
a tone starts. We waited the gap twice: libwebrtc's DtmfSender already
waits duration + gap before reporting the tone as played, and then
RTCDTMFSender::onTonePlayed() started a further interToneGap timer before
playing the next tone, so each tone took duration + 2 * interToneGap.
Play the next tone directly from onTonePlayed() and remove the timer.

[1] https://w3c.github.io/webrtc-pc/#dom-RTCDTMFSender-insertDTMF

* LayoutTests/imported/w3c/web-platform-tests/webrtc/RTCDTMFSender-ontonechange-long.https.html: Added new tests
* LayoutTests/imported/w3c/web-platform-tests/webrtc/RTCDTMFSender-ontonechange-long.https-expected.txt: Updated Expectation
* Source/WebCore/Modules/mediastream/RTCDTMFSender.cpp:
(WebCore::RTCDTMFSender::RTCDTMFSender):
(WebCore::RTCDTMFSender::insertDTMF):
(WebCore::RTCDTMFSender::onTonePlayed):
(WebCore::RTCDTMFSender::stop):
(WebCore::RTCDTMFSender::toneTimerFired): Deleted.
* Source/WebCore/Modules/mediastream/RTCDTMFSender.h:

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