Fix front-end host creation upon navigation
- when navigating, add host bindings to the pending frame rather than old frame;
- force renderer swap if front-end URL is invalid;
- move front-end URL validation to DevToolsUIBindingds
This also re-lands https://codereview.chromium.org/2607833002
BUG=662859,678035
Review-Url: https://codereview.chromium.org/2620153002
Cr-Commit-Position: refs/heads/master@{#442781}
(cherry picked from commit c2db881506f5709433a5bf6ed981b1bc0c860598)
Review-Url: https://codereview.chromium.org/2653783003 .
Cr-Commit-Position: refs/branch-heads/2924@{#853}
Cr-Branched-From: 3a87aecc31cd1ffe751dd72c04e5a96a1fc8108a-refs/heads/master@{#433059}
11 files changed
