GitLab

This CL fleshes out the basic architecture of the spy. Introducing SpyServerImpl and enough code to operate the "start" and "stop" commands of the front-end.

Still a quite a few loose ends, specially on teardown.

I updated the design doc to reflect this CL:
https://docs.google.com/a/chromium.org/document/d/11FKYXf9mSohlsgl4JmGlyWE1ScX3DKdssdjub63tkwA/edit?usp=sharing


BUG=360188
TEST=manual via test/spy_repl_test.html

Review URL: https://codereview.chromium.org/284743002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@272458 0039d316-1c4b-4281-b951-d872f2087c98