Create isolation target for WebView CTS tests and capture gn-paths arg in pydeps.

The isolation target will be used by swarming, the gn-paths arg was not being
captured in pydeps files generated with build/print_python_deps.py, but it is
needed by the isolation target to properly locate its depenencies.

Bug: 803245
Change-Id: I15bf4c8f7d1cd24a6ce1fcb4b44aeeff42786943
Reviewed-on: https://chromium-review.googlesource.com/1234340
Commit-Queue: Andrew Luo <[email protected]>
Reviewed-by: Changwan Ryu <[email protected]>
Reviewed-by: agrieve <[email protected]>
Reviewed-by: John Budorick <[email protected]>
Cr-Commit-Position: refs/heads/master@{#592899}
4 files changed