use document.scrollingElement

Former-commit-id: 7f6d3a004c9e151091de7c9069b1410f254e82da

lib/hooks/content/content-hooks-frames-web.js

@@ -49,19 +49,20 @@
 	let loadDeferredImages;
 
 	addEventListener(LOAD_DEFERRED_IMAGES_START_EVENT, () => {
-		const clientHeight = document.documentElement.clientHeight;
-		const clientWidth = document.documentElement.clientWidth;
-		const scrollHeight = Math.max(document.documentElement.scrollHeight - (clientHeight * .5), clientHeight);
-		const scrollWidth = Math.max(document.documentElement.scrollWidth - (clientWidth * .5), clientWidth);
-		document.documentElement.__defineGetter__("clientHeight", () => scrollHeight);
-		document.documentElement.__defineGetter__("clientWidth", () => scrollWidth);
+		const scrollingElement = document.scrollingElement || document.documentElement;
+		const clientHeight = scrollingElement.clientHeight;
+		const clientWidth = scrollingElement.clientWidth;
+		const scrollHeight = Math.max(scrollingElement.scrollHeight - (clientHeight * .5), clientHeight);
+		const scrollWidth = Math.max(scrollingElement.scrollWidth - (clientWidth * .5), clientWidth);
+		scrollingElement.__defineGetter__("clientHeight", () => scrollHeight);
+		scrollingElement.__defineGetter__("clientWidth", () => scrollWidth);
 		screen.__defineGetter__("height", () => scrollHeight);
 		screen.__defineGetter__("width", () => scrollWidth);
 		if (!window._singleFile_getBoundingClientRect) {
 			window._singleFile_getBoundingClientRect = Element.prototype.getBoundingClientRect;
 			Element.prototype.getBoundingClientRect = function () {
 				const boundingRect = window._singleFile_getBoundingClientRect.call(this);
-				if (this == document.documentElement) {
+				if (this == scrollingElement) {
 					boundingRect.__defineGetter__("height", () => scrollHeight);
 					boundingRect.__defineGetter__("bottom", () => scrollHeight + boundingRect.top);
 					boundingRect.__defineGetter__("width", () => scrollWidth);
@@ -124,8 +125,9 @@
 
 
 	addEventListener(LOAD_DEFERRED_IMAGES_END_EVENT, () => {
-		delete document.documentElement.clientHeight;
-		delete document.documentElement.clientWidth;
+		const scrollingElement = document.scrollingElement || document.documentElement;
+		delete scrollingElement.clientHeight;
+		delete scrollingElement.clientWidth;
 		delete screen.height;
 		delete screen.width;
 		if (window._singleFile_getBoundingClientRect) {
@@ -177,7 +179,8 @@
 
 	addEventListener(LOAD_DEFERRED_IMAGES_START_EVENT, () => {
 		loadDeferredImages = true;
-		const docBoundingRect = document.documentElement.getBoundingClientRect();
+		const scrollingElement = document.scrollingElement || document.documentElement;
+		const docBoundingRect = scrollingElement.getBoundingClientRect();
 		Array.from(observers, ([intersectionObserver, observer]) => {
 			const rootBoundingRect = observer.options.root && observer.options.root.getBoundingClientRect();
 			observer.callback(observedElements.get(intersectionObserver).map(target => {