DevTools: hoist debugger paused reason to top

This interface change moves the paused reason (e.g. paused on breakpoint, paused
on subtree modification, etc) message to the top of the sources panel.  See bug
for screenshots.

BUG=572068

Review-Url: https://codereview.chromium.org/2389883003
Cr-Commit-Position: refs/heads/master@{#427553}
20 files changed