Further merge and reduce

- Remove unused keyboardEvent module
- Trim unused browserEvent in OnStopCallback
- Inline single-use helpers to reduce module surface
- Remove createFastDomNode wrapper

src/browser/scrollable/mouseEvent.ts

@@ -3,9 +3,100 @@
  *  Licensed under the MIT License. See License.txt in the project root for license information.
  *--------------------------------------------------------------------------------------------*/
 
-import { IframeUtils } from './iframe';
 import * as platform from 'common/Platform';
 
+interface IWindowChainElement {
+  readonly window: WeakRef<Window>;
+  readonly iframeElement: Element | null;
+}
+
+const sameOriginWindowChainCache = new WeakMap<Window, IWindowChainElement[] | null>();
+
+function getParentWindowIfSameOrigin(w: Window): Window | null {
+  if (!w.parent || w.parent === w) {
+    return null;
+  }
+
+  try {
+    const location = w.location;
+    const parentLocation = w.parent.location;
+    if (location.origin !== 'null' && parentLocation.origin !== 'null' && location.origin !== parentLocation.origin) {
+      return null;
+    }
+  } catch {
+    return null;
+  }
+
+  return w.parent;
+}
+
+class IframeUtils {
+
+  private static _getSameOriginWindowChain(targetWindow: Window): IWindowChainElement[] {
+    let windowChainCache = sameOriginWindowChainCache.get(targetWindow);
+    if (!windowChainCache) {
+      windowChainCache = [];
+      sameOriginWindowChainCache.set(targetWindow, windowChainCache);
+      let w: Window | null = targetWindow;
+      let parent: Window | null;
+      do {
+        parent = getParentWindowIfSameOrigin(w);
+        if (parent) {
+          windowChainCache.push({
+            window: new WeakRef(w),
+            iframeElement: w.frameElement ?? null
+          });
+        } else {
+          windowChainCache.push({
+            window: new WeakRef(w),
+            iframeElement: null
+          });
+        }
+        w = parent;
+      } while (w);
+    }
+    return windowChainCache.slice(0);
+  }
+
+  public static getPositionOfChildWindowRelativeToAncestorWindow(childWindow: Window, ancestorWindow: Window | null): { top: number, left: number } {
+
+    if (!ancestorWindow || childWindow === ancestorWindow) {
+      return {
+        top: 0,
+        left: 0
+      };
+    }
+
+    let top = 0;
+    let left = 0;
+
+    const windowChain = this._getSameOriginWindowChain(childWindow);
+
+    for (const windowChainEl of windowChain) {
+      const windowInChain = windowChainEl.window.deref();
+      top += windowInChain?.scrollY ?? 0;
+      left += windowInChain?.scrollX ?? 0;
+
+      if (windowInChain === ancestorWindow) {
+        break;
+      }
+
+      if (!windowChainEl.iframeElement) {
+        break;
+      }
+
+      const boundingRect = windowChainEl.iframeElement.getBoundingClientRect();
+      top += boundingRect.top;
+      left += boundingRect.left;
+    }
+
+    return {
+      top: top,
+      left: left
+    };
+  }
+}
+
 export interface IMouseEvent {
   readonly browserEvent: MouseEvent;
   readonly leftButton: boolean;