Add OWNERS for Start surface files outside of the folder

Some files that are often touched by Start surface are located outside
of the start_surface or tab_ui folders. Add some per-file owners to
streamline code review.

Bug: None
Change-Id: Ie4973fff3616521d95fcb150e6e9511132484422
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2267506
Commit-Queue: Wei-Yin Chen (陳威尹) <wychen@chromium.org>
Commit-Queue: Theresa  <twellington@chromium.org>
Auto-Submit: Wei-Yin Chen (陳威尹) <wychen@chromium.org>
Reviewed-by: Theresa  <twellington@chromium.org>
Cr-Commit-Position: refs/heads/master@{#782643}

chrome/android/java/src/org/chromium/chrome/browser/compositor/layouts/OWNERS

 per-file Layout*=mdjones@chromium.org
+per-file OverviewMode*=file://chrome/android/java/src/org/chromium/chrome/browser/tasks/OWNERS

chrome/android/java/src/org/chromium/chrome/browser/toolbar/OWNERS

@@ -3,5 +3,7 @@ tedchoc@chromium.org
 yusufo@chromium.org
 twellington@chromium.org
 
+per-file TabSwitcher*=file://chrome/android/java/src/org/chromium/chrome/browser/tasks/OWNERS
+
 # COMPONENT: UI>Browser>Toolbar
 # OS: Android

chrome/android/java/src/org/chromium/chrome/browser/toolbar/top/OWNERS

+per-file StartSurfaceToolbar*=file://chrome/android/java/src/org/chromium/chrome/browser/tasks/OWNERS