don't use __defineGetter__ to override FontFace and IntersectionObserver (fix #164)

lib/hooks/hooks-frame.js

@@ -244,18 +244,18 @@ this.hooksFrame = this.hooksFrame || (() => {
 		};
 		window.cancelAnimationFrame.toString = function () { return "cancelAnimationFrame() { [native code] }"; };
 
-		const FontFace = window.FontFace;
-		let warningFontFaceDisplayed;
-		window.__defineGetter__("FontFace", () => new Proxy(FontFace, {
-			construct(FontFace, argumentsList) {
+		if (window.FontFace) {
+			const FontFace = window.FontFace;
+			let warningFontFaceDisplayed;
+			window.FontFace = function () {
 				if (!warningFontFaceDisplayed) {
 					console.warn("SingleFile is hooking the FontFace constructor to get font URLs."); // eslint-disable-line no-console
 					warningFontFaceDisplayed = true;
 				}
 				const detail = {};
-				detail["font-family"] = argumentsList[0];
-				detail.src = argumentsList[1];
-				const descriptors = argumentsList[2];
+				detail["font-family"] = arguments[0];
+				detail.src = arguments[1];
+				const descriptors = arguments[2];
 				if (descriptors) {
 					Object.keys(descriptors).forEach(descriptor => {
 						if (FONT_STYLE_PROPERTIES[descriptor]) {
@@ -273,50 +273,47 @@ this.hooksFrame = this.hooksFrame || (() => {
 				} else {
 					dispatchEvent(new CustomEvent(NEW_FONT_FACE_EVENT, { detail }));
 				}
-				return new FontFace(...argumentsList);
-			}
-		}));
+				return new FontFace(...arguments);
+			};
+		}
 
 		if (window.IntersectionObserver) {
 			const IntersectionObserver = window.IntersectionObserver;
 			const observeIntersection = IntersectionObserver.prototype.observe;
 			const unobserveIntersection = IntersectionObserver.prototype.unobserve;
 			let warningIntersectionObserverDisplayed;
-			window.__defineGetter__("IntersectionObserver", () => new Proxy(IntersectionObserver, {
-				construct(IntersectionObserver, argumentsList) {
-					if (!warningIntersectionObserverDisplayed) {
-						console.warn("SingleFile is hooking the IntersectionObserver API to detect and load deferred images."); // eslint-disable-line no-console
-						warningRequestAnimationFrameDisplayed = true;
+			window.IntersectionObserver = function () {
+				if (!warningIntersectionObserverDisplayed) {
+					console.warn("SingleFile is hooking the IntersectionObserver API to detect and load deferred images."); // eslint-disable-line no-console
+					warningRequestAnimationFrameDisplayed = true;
+				}
+				const intersectionObserver = new IntersectionObserver(...arguments);
+				const callback = arguments[0];
+				const options = arguments[1];
+				intersectionObserver.observe = function (targetElement) {
+					let targetElements = observedElements.get(intersectionObserver);
+					if (!targetElements) {
+						targetElements = [];
+						observedElements.set(intersectionObserver, targetElements);
 					}
-					const intersectionObserver = new IntersectionObserver(...argumentsList);
-					const callback = argumentsList[0];
-					const options = argumentsList[1];
-					intersectionObserver.observe = function (targetElement) {
-						let targetElements = observedElements.get(intersectionObserver);
-						if (!targetElements) {
-							targetElements = [];
+					targetElements.push(targetElement);
+					return observeIntersection.call(intersectionObserver, targetElement);
+				};
+				intersectionObserver.unobserve = function (targetElement) {
+					let targetElements = observedElements.get(intersectionObserver);
+					if (targetElements) {
+						targetElements = targetElements.filter(element => element <= targetElement);
+						if (targetElements.length) {
 							observedElements.set(intersectionObserver, targetElements);
+						} else {
+							observedElements.delete(intersectionObserver);
 						}
-						targetElements.push(targetElement);
-						return observeIntersection.call(intersectionObserver, targetElement);
-					};
-					intersectionObserver.unobserve = function (targetElement) {
-						let targetElements = observedElements.get(intersectionObserver);
-						if (targetElements) {
-							targetElements = targetElements.filter(element => element <= targetElement);
-							if (targetElements.length) {
-								observedElements.set(intersectionObserver, targetElements);
-							} else {
-								observedElements.delete(intersectionObserver);
-							}
-						}
-						return unobserveIntersection.call(intersectionObserver, targetElement);
-					};
-					observers.set(intersectionObserver, { callback, options });
-					return intersectionObserver;
-				}
-			}));
-			window.__defineSetter__("IntersectionObserver", () => { });
+					}
+					return unobserveIntersection.call(intersectionObserver, targetElement);
+				};
+				observers.set(intersectionObserver, { callback, options });
+				return intersectionObserver;
+			};
 		}
 	}