WebUI Tab Strip: Increase minimum velocity for tab swiping

This is based off of feedback from UX research suggesting that the
swipe to close tab gesture was too easy to trigger accidentally.

Change-Id: I20ce1602037dea85326288ac565877d2882ddc3f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2291231Reviewed-by: dpapad <dpapad@chromium.org>
Commit-Queue: John Lee <johntlee@chromium.org>
Cr-Commit-Position: refs/heads/master@{#787845}

chrome/browser/resources/tab_strip/tab_swiper.js

@@ -34,7 +34,7 @@ export const SWIPE_FINISH_THRESHOLD_PX = 200;
  * register the set of pointer events as an intended swipe.
  * @const {number}
  */
-const SWIPE_VELOCITY_THRESHOLD = 0.1;
+const SWIPE_VELOCITY_THRESHOLD = 0.2;
 
 export class TabSwiper {
   /** @param {!HTMLElement} element */