fix: font face descriptors in chrome 38 (#490)

In chrome 38 if some attribute is undefined the font is not loaded

Author: wouterlucas

src/core/text-rendering/font-face-types/WebTrFontFace.ts

@@ -49,7 +49,7 @@ export class WebTrFontFace extends TrFontFace {
     const determinedDescriptors = this.descriptors;
 
     // Convert TrFontFaceDescriptors to CSS FontFaceDescriptors
-    const cssDescriptors: FontFaceDescriptors = {
+    let cssDescriptors: FontFaceDescriptors = {
       style: determinedDescriptors.style,
       weight:
         typeof determinedDescriptors.weight === 'number'
@@ -61,6 +61,13 @@ export class WebTrFontFace extends TrFontFace {
       display: determinedDescriptors.display,
     };
 
+    for (const k in cssDescriptors) {
+      const key = k as keyof FontFaceDescriptors;
+      if (cssDescriptors[key] === undefined) {
+        delete cssDescriptors[key];
+      }
+    }
+
     const fontFace = new FontFace(
       fontFamily,
       `url(${fontUrlWithoutParentheses})`,
@@ -71,14 +78,12 @@ export class WebTrFontFace extends TrFontFace {
       fontFace
         .load()
         .then(() => {
-          // eslint-disable-next-line @typescript-eslint/no-unnecessary-type-assertion
           (this.loaded as boolean) = true;
           this.emit('loaded');
         })
         .catch(console.error);
     } else {
       // Default font
-      // eslint-disable-next-line @typescript-eslint/no-unnecessary-type-assertion
       (this.loaded as boolean) = true;
       this.emit('loaded');
     }