Add UMA action for tabgroup creation

This is a UMA action that was added for HTS, but is missing from GTS.
It triggers when the user creates a group via the "Create Group" button
inside the tab switcher.

BUG=952478

Change-Id: Ic5a7b090906ac979da77e633a6c9fd9afc2e8c58
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1566718Reviewed-by: Ted Choc <tedchoc@chromium.org>
Commit-Queue: Yusuf Ozuysal <yusufo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#650525}

chrome/android/features/tab_ui/java/src/org/chromium/chrome/browser/tasks/tab_management/GridTabSwitcherMediator.java

@@ -254,6 +254,7 @@ class GridTabSwitcherMediator
             mTabModelSelector.openNewTab(new LoadUrlParams(UrlConstants.NTP_URL),
                     TabLaunchType.FROM_CHROME_UI, parentTab,
                     mTabModelSelector.isIncognitoSelected());
+            RecordUserAction.record("TabGroup.Created.TabSwitcher");
         };
     }