refactor: remove any type from ts4.4 upgrade regarding

Removes the `any` type used in the previous ts4.4 upgrade PR when
refering to the style property on the element. Creates a new type to
work around the built in `CSSStyleDeclaration` not including
`webkitTapHighlightColor`.

Author: zarend

src/cdk/drag-drop/drag-ref.ts

@@ -24,6 +24,7 @@ import {DropListRefInternal as DropListRef} from './drop-list-ref';
 import {DragDropRegistry} from './drag-drop-registry';
 import {
   combineTransforms,
+  DragCSSStyleDeclaration,
   extendStyles,
   toggleNativeDragInteractions,
   toggleVisibility,
@@ -756,7 +757,8 @@ export class DragRef<T = any> {
     this._toggleNativeDragInteractions();
 
     if (this._handles) {
-      (this._rootElement.style as any).webkitTapHighlightColor = this._rootElementTapHighlight;
+      (this._rootElement.style as DragCSSStyleDeclaration).webkitTapHighlightColor =
+        this._rootElementTapHighlight;
     }
 
     if (!this._hasStartedDragging) {
@@ -884,7 +886,7 @@ export class DragRef<T = any> {
     // otherwise iOS will still add it, even though all the drag interactions on the handle
     // are disabled.
     if (this._handles.length) {
-      const rootStyles = rootElement.style as any;
+      const rootStyles = rootElement.style as DragCSSStyleDeclaration;
       this._rootElementTapHighlight = rootStyles.webkitTapHighlightColor || '';
       rootStyles.webkitTapHighlightColor = 'transparent';
     }

src/cdk/drag-drop/drag-styling.ts

@@ -13,6 +13,7 @@
  export interface DragCSSStyleDeclaration extends CSSStyleDeclaration {
   msScrollSnapType: string;
   scrollSnapType: string;
+  webkitTapHighlightColor: string;
 }
 
 /**