handle missing ResizeObserver

Author: kseamon

src/cdk/table/sticky-styler.ts

@@ -34,7 +34,9 @@ export const STICKY_DIRECTIONS: StickyDirection[] = ['top', 'bottom', 'left', 'r
  */
 export class StickyStyler {
   private _elemSizeCache = new WeakMap<HTMLElement, {width: number; height: number}>();
-  private _resizeObserver = new ResizeObserver(entries => this._updateCachedSizes(entries));
+  private _resizeObserver = ResizeObserver
+    ? new ResizeObserver(entries => this._updateCachedSizes(entries))
+    : null;
   private _updatedStickyColumnsParamsToReplay: UpdateStickyColumnsParams[] = [];
   private _stickyColumnsReplayTimeout: number | null = null;
   private _cachedCellWidths: number[] = [];
@@ -448,6 +450,11 @@ export class StickyStyler {
 
     const clientRect = element.getBoundingClientRect();
     const size = {width: clientRect.width, height: clientRect.height};
+
+    if (!this._resizeObserver) {
+      return size;
+    }
+
     this._elemSizeCache.set(element, size);
     this._resizeObserver.observe(element, {box: 'border-box'});
     return size;