DevTools: Fix the way search works when switching between editor tabs.

We should perform the search in the newly selected editor after switching tabs.
We should also postpone setting selection in the editor to the moment where it has synced its sized, otherwise we mess up the scroll position.

BUG=413153
R=lushnikov@chromium.org, lushnikov

Review URL: https://codereview.chromium.org/669043002

git-svn-id: svn://svn.chromium.org/blink/trunk@184257 bbb929c8-8fbe-4397-9dbb-9b2b20218538