Revert "Do nothing in SplitWidget.showBoth if already showing"

This reverts commit 250194e.

Reason for revert: causes http://crbug.com/404476981 - "Unable to drag
the devtools while panel is at left side"

Original change's description:
> Do nothing in SplitWidget.showBoth if already showing
>
> This method resulted in some unnecessary work happening in RPP, causing
> the flame graph to respond to a "resize" event even though nothing
> changed size. Since RPP calls this often (like when activating an
> insight), this contributed to the sometimes-janky feeling caused by
> opening an insight taking too long.
>
> Bug: 40278532
> Change-Id: I43b4d4e7a9b400cd3edf06f3f606e008b6455c2d
> Reviewed-on: https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/6221819
> Commit-Queue: Connor Clark <[email protected]>
> Reviewed-by: Paul Irish <[email protected]>

Bug: 40278532, 404476981
Change-Id: I1b144d662dd537d397c6c61c6abc1ae9be3c5d4a
Reviewed-on: https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/6369954
Reviewed-by: Paul Irish <[email protected]>
Commit-Queue: Connor Clark <[email protected]>

Author: Connor Clark

front_end/ui/legacy/SplitWidget.ts

@@ -397,11 +397,6 @@ export class SplitWidget extends Common.ObjectWrapper.eventMixin<EventTypes, typ
   }
 
   showBoth(animate?: boolean): void {
-    // Do nothing if both components are already showing.
-    if (!this.mainElement.classList.contains('hidden') && !this.sidebarElementInternal.classList.contains('hidden')) {
-      return;
-    }
-
     if (this.showModeInternal === ShowMode.BOTH) {
       animate = false;
     }