matTooltip jumps in conjuction with cdk-virtual-scroll-viewport

#### What is the expected behavior?
The tooltip should remain in place when the target is replaced.

#### What is the current behavior?
The tooltip jumps to the bottom of the page.

#### What are the steps to reproduce?
There are 2 lists rendered (refreshed at 2 seconds), the bug can be seen in the first one:
- hover over the first item from the first list; you'll notice the tooltip jumps to the bottom of the page

If you hover over the first item in the second list it behaves correctly.
The second list has `templateCacheSize: 0`

https://stackblitz.com/edit/virtual-scroll-bug?file=src%2Fapp%2Fapp.component.html

#### Which versions of Angular, Material, OS, TypeScript, browsers are affected?
Angular 7.2.11 (latest)
Material 7.3.6 (latest)
OS: macOS Mojave 10.14.3


Start with the linked StackBlitz reproduction, especially src/app/app.component.html, and compare the two cdk-virtual-scroll-viewport lists and their templateCacheSize settings. Reproduce the two-second refresh while hovering the first item; done means the matTooltip remains in place when its target is replaced rather than jumping to the bottom of the page.

Written by the indexing model from the issue text.