It currently looks like the `map.get(element)` returns `undefined` even for previously-loaded elements. Are we evicting from the cache prematurely? Why?

Our second level caching (inside of `parseHookNames`) is working but this is still resulting in a lot of unnecessary work.
if (__DEBUG__) {
      console.log(
        'extractAndLoadSourceMaps() Initializing source-map library ...',
      );
    }
    
    const wasmMappingsURL = chrome.extension.getURL('mappings.wasm');
    SourceMapConsumer.initialize({'lib/mappings.wasm': wasmMappingsURL});
  }
  
  const fetchPromises = new Map();
  const setPromises = [];
  locationKeyToHookSourceData.forEach(hookSourceData => {
    if (hookSourceData.sourceConsumer != null) {
      
      return;
    }
    const runtimeSourceCode = ((hookSourceData.runtimeSourceCode: any): string);
    const sourceMappingURLs = runtimeSourceCode.match(SOURCE_MAP_REGEX);
    if (sourceMappingURLs == null) {
      
      if (__DEBUG__) {
        console.log('extractAndLoadSourceMaps() No source map found');
      }
    } else {