Do not use function name to track components (#6542)

UglifyJS2 is allowed to mangle function names, and function names can also
be duplicate if they are from different scopes. Therefore function names
are not reliable as identifiers.

Functions as keys for Map object is a cheaper and more reliable
alternative.

app/javascript/mastodon/features/ui/components/bundle.js

@@ -26,7 +26,7 @@ class Bundle extends React.Component {
     onFetchFail: noop,
   }
 
-  static cache = {}
+  static cache = new Map
 
   state = {
     mod: undefined,
@@ -51,13 +51,12 @@ class Bundle extends React.Component {
 
   load = (props) => {
     const { fetchComponent, onFetch, onFetchSuccess, onFetchFail, renderDelay } = props || this.props;
+    const cachedMod = Bundle.cache.get(fetchComponent);
 
     onFetch();
 
-    if (Bundle.cache[fetchComponent.name]) {
+    if (cachedMod) {
-      const mod = Bundle.cache[fetchComponent.name];
+      this.setState({ mod: cachedMod.default });
-
-      this.setState({ mod: mod.default });
       onFetchSuccess();
       return Promise.resolve();
     }
@@ -71,7 +70,7 @@ class Bundle extends React.Component {
 
     return fetchComponent()
       .then((mod) => {
-        Bundle.cache[fetchComponent.name] = mod;
+        Bundle.cache.set(fetchComponent, mod);
         this.setState({ mod: mod.default });
         onFetchSuccess();
       })