Malformed PortRange or ThirdPartyAuthConfig should trigger OnPolicyError.

Before this change a malformed value of RemoteAccessHostUdpPortRange policy
(i.e. "123456-blah") was ignored and a default value was used.  Similarily for
the 3 third-party-auth-config policies (RemoteAccessHostTokenUrl,
...TokenValidationUrl and ...TokenValidationCertificateIssuer) we were falling
back to a secure default, but not reporting a policy error.  After this change
such malformed values will trigger an OnPolicyError callback.

Notes:
- Guaranteeing that PolicyWatcher always returns valid policy values, removes
  the need for a "rejecting" Me2MeHostAuthenticatorFactory.
- Moving PortRange and ThirdPartyAuthConfig to separate compilation units
  helps readability elsewhere + encourages better unit tests coverage.
- Initially I tried to wrap all policies in a new ChromotingPolicies class,
  but eventually went back to prevalidating and passing base::DictionaryValue.
  - Arguments for using ChromotingPolicies:
    - Helps avoid overtesting in policy_watcher_unittests.cc (i.e. helps focus
      the tests on a single policy value).
  - Arguments for using base::DictionaryValue:
    - Minimizes changes.
    - Keeps things simple (as opposed to having to introduce a custom
      equivalent of optional<T> [nothing similar present in Chromium AFAICT]).
  - Neutral:
    - Strong-typing of ChromotingPolicies didn't help readability as much as I
      expected and hoped for.

BUG=427513
TEST=remoting_unittests

Review URL: https://codereview.chromium.org/966433002

Cr-Commit-Position: refs/heads/master@{#318910}

1 files changed, 2 insertions, 0 deletions

diff --git a/remoting/remoting_host_srcs.gypi b/remoting/remoting_host_srcs.gypi
index 9c99640..15d3eb0 100644
--- a/remoting/remoting_host_srcs.gypi
+++ b/remoting/remoting_host_srcs.gypi
@@ -218,6 +218,8 @@
       'host/single_window_input_injector_linux.cc',
       'host/single_window_input_injector_mac.cc',
       'host/single_window_input_injector_win.cc',
+      'host/third_party_auth_config.cc',
+      'host/third_party_auth_config.h',
       'host/token_validator_base.cc',
       'host/token_validator_base.h',
       'host/token_validator_factory_impl.cc',