Fix Closure breaking AUDIO_WORKLET (emscripten-core#22472)

If building with `-sAUDIO_WORKLET` and `--closure=1` the generated glue
JS will minimise the property names passed to the worklet's message
handler:

https://github.com/emscripten-core/emscripten/blob/9445d6a1c3e3872d6e909565301a47c9c4fbd35b/src/audio_worklet.js#L179
E.g. these are received as:
```
A: 3,
B: 1,
F: 0,
s: "noise-generator"
```
No sound will be generated as a result, since calls to
`emscripten_create_wasm_audio_worklet_processor_async()` will never call
the passed function.

Author: cwoffenden

src/audio_worklet.js

@@ -168,18 +168,22 @@ class BootstrapMessages extends AudioWorkletProcessor {
         }
 #endif
         // Register a real AudioWorkletProcessor that will actually do audio processing.
-        registerProcessor(d['_wpn'], createWasmAudioWorkletProcessor(d['audioParams']));
+        // 'ap' being the audio params
+        registerProcessor(d['_wpn'], createWasmAudioWorkletProcessor(d['ap']));
 #if WEBAUDIO_DEBUG
-        console.log(`Registered a new WasmAudioWorkletProcessor "${d['_wpn']}" with AudioParams: ${d['audioParams']}`);
+        console.log(`Registered a new WasmAudioWorkletProcessor "${d['_wpn']}" with AudioParams: ${d['ap']}`);
 #endif
         // Post a Wasm Call message back telling that we have now registered the
-        // AudioWorkletProcessor class, and should trigger the user onSuccess
-        // callback of the
-        // emscripten_create_wasm_audio_worklet_processor_async() call.
-        p.postMessage({'_wsc': d['callback'], 'x': [d['contextHandle'], 1/*EM_TRUE*/, d['userData']] }); // "WaSm Call"
-      } else if (d['_wsc']) {
+        // AudioWorkletProcessor, and should trigger the user onSuccess callback
+        // of the emscripten_create_wasm_audio_worklet_processor_async() call.
+        //
         // '_wsc' is short for 'wasm call', using an identifier that will never
         // conflict with user messages
+        // 'cb' the callback function
+        // 'ch' the context handle
+        // 'ud' the passed user data
+        p.postMessage({'_wsc': d['cb'], 'x': [d['ch'], 1/*EM_TRUE*/, d['ud']] });
+      } else if (d['_wsc']) {
         Module['wasmTable'].get(d['_wsc'])(...d['x']);
       };
     }

src/library_webaudio.js

@@ -122,9 +122,12 @@ let LibraryWebAudio = {
   },
 
 #if AUDIO_WORKLET
+  // emscripten_start_wasm_audio_worklet_thread_async() doesn't use stackAlloc,
+  // etc., but the created worklet does.
   emscripten_start_wasm_audio_worklet_thread_async__deps: [
     '$_wasmWorkersID',
-    '$_EmAudioDispatchProcessorCallback'],
+    '$_EmAudioDispatchProcessorCallback',
+    '$stackAlloc', '$stackRestore', '$stackSave'],
   emscripten_start_wasm_audio_worklet_thread_async: (contextHandle, stackLowestAddress, stackSize, callback, userData) => {
 
 #if ASSERTIONS
@@ -249,14 +252,15 @@ let LibraryWebAudio = {
 #endif
 
     EmAudio[contextHandle].audioWorklet.bootstrapMessage.port.postMessage({
-      // '_wpn' == 'Worklet Processor Name', use a deliberately mangled name so
-      // that this field won't accidentally be mixed with user submitted
-      // messages.
-      _wpn: UTF8ToString(HEAPU32[options]),
-      audioParams,
-      contextHandle,
-      callback,
-      userData
+      // Deliberately mangled and short names used here ('_wpn', the 'Worklet
+      // Processor Name' used as a 'key' to verify the message type so as to
+      // not get accidentally mixed with user submitted messages, the remainder
+      // for space saving reasons, abbreviated from their variable names).
+      '_wpn': UTF8ToString(HEAPU32[options]),
+      'ap': audioParams,
+      'ch': contextHandle,
+      'cb': callback,
+      'ud': userData
     });
   },
 

src/runtime_shared.js

@@ -13,7 +13,7 @@
     if (!shouldExport) {
       if (MODULARIZE && EXPORT_ALL) {
         shouldExport = true;
-      } else if (AUDIO_WORKLET && (x == 'HEAP32' || x == 'HEAPU32')) {
+      } else if (AUDIO_WORKLET && (x == 'HEAPU32' || x == 'HEAPF32')) {
         // Export to the AudioWorkletGlobalScope the needed variables to access
         // the heap. AudioWorkletGlobalScope is unable to access global JS vars
         // in the compiled main JS file.