<refactor>: Prepare for TypeScript v3.2.2 (#14847)

We're upgrading TypeScript to v3.2.2 in google3. This PR suppresses the
compilation errors without actually upgrading the version of TypeScript.

According to the comments, the top and bottom properties in
ExtendedScrollToOptions are mutually exclusive. However when rewriting
the bottom offset as a top offset both properties are defined. With the
improved type inference in TypeScript 3.2 this is now a compilation
error.

Author: bowenni

src/cdk/scrolling/scrollable.ts

@@ -95,13 +95,15 @@ export class CdkScrollable implements OnInit, OnDestroy {
 
     // Rewrite the bottom offset as a top offset.
     if (options.bottom != null) {
-      options.top = el.scrollHeight - el.clientHeight - options.bottom;
+      (options as _Without<_Bottom> & _Top).top =
+          el.scrollHeight - el.clientHeight - options.bottom;
     }
 
     // Rewrite the right offset as a left offset.
     if (isRtl && getRtlScrollAxisType() != RtlScrollAxisType.NORMAL) {
       if (options.left != null) {
-        options.right = el.scrollWidth - el.clientWidth - options.left;
+        (options as _Without<_Left> & _Right).right =
+            el.scrollWidth - el.clientWidth - options.left;
       }
 
       if (getRtlScrollAxisType() == RtlScrollAxisType.INVERTED) {
@@ -111,7 +113,8 @@ export class CdkScrollable implements OnInit, OnDestroy {
       }
     } else {
       if (options.right != null) {
-        options.left = el.scrollWidth - el.clientWidth - options.right;
+        (options as _Without<_Right> & _Left).left =
+            el.scrollWidth - el.clientWidth - options.right;
       }
     }