[DevTools] Avoid current_ and pending_ being the same host in RenderFrameDevToolsAgentHost.

This happens when we resue RenderFrameHost after crash.
The fix is to commit immediately to avoid pending. This is safe because
we don't even have two RenderFrameHosts.

BUG=644963

Review-Url: https://codereview.chromium.org/2366773003
Cr-Commit-Position: refs/heads/master@{#421697}
3 files changed