Try dummy audio for FF; remove LACKS_SOUND_HARDWARE

Author: cwoffenden

.circleci/config.yml

@@ -306,15 +306,16 @@ commands:
       - run:
           name: run tests (<< parameters.title >>)
           environment:
-            EMTEST_LACKS_SOUND_HARDWARE: "1"
             EMTEST_DETECT_TEMPFILE_LEAKS: "0"
             # --no-sandbox because we are running as root and chrome requires
             # this flag for now: https://crbug.com/638180
             CHROME_FLAGS_BASE: "--no-first-run -start-maximized --no-sandbox --use-gl=swiftshader --user-data-dir=/tmp/chrome-emscripten-profile --enable-experimental-web-platform-features"
             CHROME_FLAGS_HEADLESS: "--headless=new --remote-debugging-port=1234"
             CHROME_FLAGS_WASM: "--enable-experimental-webassembly-features --js-flags=\"--experimental-wasm-stack-switching --experimental-wasm-type-reflection\""
             CHROME_FLAGS_NOCACHE: "--disk-cache-dir=/dev/null --disk-cache-size=1 --media-cache-size=1 --disable-application-cache --incognito"
-            CHROME_FLAGS_AUDIO: "--autoplay-policy=no-user-gesture-required --use-fake-device-for-media-stream"
+            # The runners lack sound hardware so fallback to a dummy device (and
+            # bypass the user gesture so audio tests work without interaction)
+            CHROME_FLAGS_AUDIO: " --use-fake-device-for-media-stream --autoplay-policy=no-user-gesture-required"
           command: |
             export EMTEST_BROWSER="/usr/bin/google-chrome $CHROME_FLAGS_BASE $CHROME_FLAGS_HEADLESS $CHROME_FLAGS_WASM $CHROME_FLAGS_NOCACHE $CHROME_FLAGS_AUDIO"
             # There are tests in the browser test suite that using libraries
@@ -361,6 +362,7 @@ commands:
             user_pref("javascript.options.shared_memory", true);
             user_pref("javascript.options.wasm_memory64", true);
             user_pref("dom.postMessage.sharedArrayBuffer.bypassCOOP_COEP.insecure.enabled", true);
+            user_pref("media.navigator.streams.fake", true);
             user_pref("media.autoplay.default", 0);
             EOF
       - run:
@@ -371,11 +373,12 @@ commands:
             #       support in headless mode) resolves
             EMTEST_LACKS_GRAPHICS_HARDWARE: "1"
             EMTEST_LACKS_WEBGPU: "1"
-            EMTEST_LACKS_SOUND_HARDWARE: "1"
             # OffscreenCanvas support is not yet done in Firefox.
             EMTEST_LACKS_OFFSCREEN_CANVAS: "1"
             EMTEST_DETECT_TEMPFILE_LEAKS: "0"
             DISPLAY: ":0"
+            # Note: as per Chrome, the FF profile enables a dummy audio device
+            # (so doesn't need the EMTEST_LACKS_SOUND_HARDWARE var)
           command: |
             export EMTEST_BROWSER="$HOME/firefox/firefox -headless -profile $HOME/tmp-firefox-profile/"
             # There are tests in the browser test suite that using libraries