feat(BrowserCapabilities) drop supportsVideo

It has been `true` for a very long time.

css/modals/video-quality/_video-quality.scss

 .video-quality-dialog {
-    .hide-warning {
-        height: 0;
-        visibility: hidden;
-    }
-
     .video-quality-dialog-title {
         margin-bottom: 10px;
     }
             word-spacing: unset;
         }
     }
-
-    &.video-not-supported {
-        .video-quality-dialog-labels {
-            color: gray;
-        }
-
-        .video-quality-dialog-slider {
-            @mixin sliderTrackDisabledStyles() {
-                background: rgba(14, 22, 36, 0.1);
-            }
-
-            &::-ms-track {
-                @include sliderTrackDisabledStyles();
-            }
-
-            &::-moz-range-track {
-                @include sliderTrackDisabledStyles();
-            }
-
-            &::-webkit-slider-runnable-track {
-                @include sliderTrackDisabledStyles();
-            }
-        }
-    }
 }
 
 .modal-dialog-form {

lang/main.json

         "ld": "LD",
         "ldTooltip": "Viewing low definition video",
         "lowDefinition": "Low definition",
-        "onlyAudioAvailable": "Only audio is available",
-        "onlyAudioSupported": "We only support audio in this browser.",
         "sd": "SD",
         "sdTooltip": "Viewing standard definition video",
         "standardDefinition": "Standard definition"

react/features/base/media/middleware.js

 import { APP_STATE_CHANGED } from '../../mobile/background';
 import { SET_AUDIO_ONLY, setAudioOnly } from '../audio-only';
 import { isRoomValid, SET_ROOM } from '../conference';
-import JitsiMeetJS from '../lib-jitsi-meet';
 import { MiddlewareRegistry } from '../redux';
 import { getPropertyValue } from '../settings';
 import { isLocalVideoTrackDesktop, setTrackMuted, TRACK_ADDED } from '../tracks';
     // XXX After the introduction of the "Video <-> Voice" toggle on the
     // WelcomePage, startAudioOnly is utilized even outside of
     // conferences/meetings.
-    let audioOnly;
-
-    if (JitsiMeetJS.mediaDevices.supportsVideo()) {
-        audioOnly
-            = Boolean(
-                getPropertyValue(
-                    state,
-                    'startAudioOnly',
-                    /* sources */ {
-                        // FIXME Practically, base/config is (really) correct
-                        // only if roomIsValid. At the time of this writing,
-                        // base/config is overwritten by URL params which leaves
-                        // base/config incorrect on the WelcomePage after
-                        // leaving a conference which explicitly overwrites
-                        // base/config with URL params.
-                        config: roomIsValid,
-
-                        // XXX We've already overwritten base/config with
-                        // urlParams if roomIsValid. However, settings are more
-                        // important than the server-side config. Consequently,
-                        // we need to read from urlParams anyway. We also
-                        // probably want to read from urlParams when
-                        // !roomIsValid.
-                        urlParams: true,
-
-                        // The following don't have complications around whether
-                        // they are defined or not:
-                        jwt: false,
-                        settings: true
-                    }));
-    } else {
-        // Default to audio-only if the (execution) environment does not
-        // support (sending and/or receiving) video.
-        audioOnly = true;
-    }
+    const audioOnly
+        = Boolean(
+            getPropertyValue(
+                state,
+                'startAudioOnly',
+                /* sources */ {
+                    // FIXME Practically, base/config is (really) correct
+                    // only if roomIsValid. At the time of this writing,
+                    // base/config is overwritten by URL params which leaves
+                    // base/config incorrect on the WelcomePage after
+                    // leaving a conference which explicitly overwrites
+                    // base/config with URL params.
+                    config: roomIsValid,
+
+                    // XXX We've already overwritten base/config with
+                    // urlParams if roomIsValid. However, settings are more
+                    // important than the server-side config. Consequently,
+                    // we need to read from urlParams anyway. We also
+                    // probably want to read from urlParams when
+                    // !roomIsValid.
+                    urlParams: true,
+
+                    // The following don't have complications around whether
+                    // they are defined or not:
+                    jwt: false,
+                    settings: true
+                }));
 
     sendAnalytics(createStartAudioOnlyEvent(audioOnly));
     logger.log(`Start audio only set to ${audioOnly.toString()}`);

react/features/video-quality/components/VideoQualitySlider.web.js

 // @flow
 
-import InlineMessage from '@atlaskit/inline-message';
 import React, { Component } from 'react';
 import type { Dispatch } from 'redux';
 
 import { createToolbarEvent, sendAnalytics } from '../../analytics';
 import { setAudioOnly } from '../../base/audio-only';
 import { translate } from '../../base/i18n';
-import JitsiMeetJS from '../../base/lib-jitsi-meet';
 import { connect } from '../../base/redux';
 import { setPreferredVideoQuality } from '../actions';
 import { VIDEO_QUALITY_LEVELS } from '../constants';
      */
     _sendrecvVideoQuality: Number,
 
-    /**
-     * Whether or not displaying video is supported in the current
-     * environment. If false, the slider will be disabled.
-     */
-    _videoSupported: Boolean,
-
     /**
      * Invoked to request toggling of audio only mode.
      */
      * @returns {ReactElement}
      */
     render() {
-        const { _videoSupported, t } = this.props;
+        const { t } = this.props;
         const activeSliderOption = this._mapCurrentQualityToSliderValue();
 
-        let classNames = 'video-quality-dialog';
-        let warning = null;
-
-        if (!_videoSupported) {
-            classNames += ' video-not-supported';
-            warning = this._renderAudioOnlyLockedMessage();
-        }
-
         return (
-            <div className = { classNames }>
+            <div className = { 'video-quality-dialog' }>
                 <h3 className = 'video-quality-dialog-title'>
                     { t('videoStatus.callQuality') }
                 </h3>
-                <div className = { warning ? '' : 'hide-warning' }>
-                    { warning }
-                </div>
                 <div className = 'video-quality-dialog-contents'>
                     <div className = 'video-quality-dialog-slider-container'>
                         { /* FIXME: onChange and onMouseUp are both used for
                            */ }
                         <input
                             className = 'video-quality-dialog-slider'
-                            disabled = { !_videoSupported }
                             max = { this._sliderOptions.length - 1 }
                             min = '0'
                             onChange = { this._onSliderChange }
         );
     }
 
-    /**
-     * Creates a React Element for notifying that the browser is in audio only
-     * and cannot be changed.
-     *
-     * @private
-     * @returns {ReactElement}
-     */
-    _renderAudioOnlyLockedMessage() {
-        const { t } = this.props;
-
-        return (
-            <InlineMessage
-                title = { t('videoStatus.onlyAudioAvailable') }>
-                { t('videoStatus.onlyAudioSupported') }
-            </InlineMessage>
-        );
-    }
-
     /**
      * Creates React Elements to display mock tick marks with associated labels.
      *
  *
  * @param {Object} state - The Redux state.
  * @private
- * @returns {{
- *     _audioOnly: boolean,
- *     _p2p: boolean,
- *     _sendrecvVideoQuality: number
- * }}
+ * @returns {Props}
  */
 function _mapStateToProps(state) {
     const { enabled: audioOnly } = state['features/base/audio-only'];
     return {
         _audioOnly: audioOnly,
         _p2p: p2p,
-        _sendrecvVideoQuality: preferredVideoQuality,
-        _videoSupported: JitsiMeetJS.mediaDevices.supportsVideo()
+        _sendrecvVideoQuality: preferredVideoQuality
     };
 }