Remove the ability to pass in more than one font to BaseFontLoader.bind

- The only existing call-site, of this method, is never passing more than *one* font at a time anyway.
 - As far as I can remember, this functionality has never actually been used (caveat: I didn't check the git history).
 - This allows simplification of the method, especially by making use of the fact that it's now asynchronous.
 - It should be just as easy to call `BaseFontLoader.bind` from within a loop, rather than having the loop in the method itself.

src/display/api.js

@@ -1945,7 +1945,7 @@ class WorkerTransport {
             fontRegistry,
           });
 
-          this.fontLoader.bind([font]).then(() => {
+          this.fontLoader.bind(font).then(() => {
             this.commonObjs.resolve(id, font);
           });
           break;

src/display/font_loader.js

@@ -60,22 +60,10 @@ class BaseFontLoader {
     }
   }
 
-  async bind(fonts) {
-    const rules = [];
-    const fontsToLoad = [];
-    const fontLoadPromises = [];
-    const getNativeFontPromise = function(nativeFontFace) {
-      // Return a promise that is always fulfilled, even when the font fails to
-      // load.
-      return nativeFontFace.loaded.catch(function(reason) {
-        warn(`Failed to load font "${nativeFontFace.family}": ${reason}`);
-      });
-    };
-
-    for (const font of fonts) {
+  async bind(font) {
     // Add the font to the DOM only once; skip if the font is already loaded.
     if (font.attached || font.missingFile) {
-        continue;
+      return;
     }
     font.attached = true;
 
@@ -83,27 +71,30 @@ class BaseFontLoader {
       const nativeFontFace = font.createNativeFontFace();
       if (nativeFontFace) {
         this.addNativeFontFace(nativeFontFace);
-          fontLoadPromises.push(getNativeFontPromise(nativeFontFace));
+        try {
+          await nativeFontFace.loaded;
+        } catch (ex) {
+          // Return a promise that is always fulfilled, even when the font
+          // failed to load.
+          warn(`Failed to load font '${nativeFontFace.family}': '${ex}'.`);
         }
-      } else {
+      }
+      return; // The font was, asynchronously, loaded.
+    }
+
+    // !this.isFontLoadingAPISupported
     const rule = font.createFontFaceRule();
     if (rule) {
       this.insertRule(rule);
-          rules.push(rule);
-          fontsToLoad.push(font);
-        }
-      }
-    }
 
-    if (this.isFontLoadingAPISupported) {
-      return Promise.all(fontLoadPromises);
-    } else if (rules.length > 0 && !this.isSyncFontLoadingSupported) {
+      if (this.isSyncFontLoadingSupported) {
+        return; // The font was, synchronously, loaded.
+      }
       return new Promise((resolve) => {
         const request = this._queueLoadingCallback(resolve);
-        this._prepareFontLoadEvent(rules, fontsToLoad, request);
+        this._prepareFontLoadEvent([rule], [font], request);
       });
     }
-    return; // Synchronous font loading supported.
   }
 
   _queueLoadingCallback(callback) {