[DevTools] Introduce unserializableValue in RemoteObject.

It carries primitive values which cannot be JSON-stringified.
Added support for it in more places on frontend side.

BUG=631162

Review-Url: https://codereview.chromium.org/2214193002
Cr-Original-Commit-Position: refs/heads/master@{#409981}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 1a8571b602f826acc09f0e6220c04c39fb12be69
3 files changed