Add enable_vp9 option to host config.

remoting/host/remoting_me2me_host.cc

Index: remoting/host/remoting_me2me_host.cc
diff --git a/remoting/host/remoting_me2me_host.cc b/remoting/host/remoting_me2me_host.cc
index eb54ab876cc7cd2e1919a1a4dafb8b78eec3db8d..4b12f418817983bb703101fb529f59e288aa90ef 100644
--- a/remoting/host/remoting_me2me_host.cc
+++ b/remoting/host/remoting_me2me_host.cc
@@ -124,6 +124,9 @@ const char kAuthSocknameSwitchName[] = "ssh-auth-sockname";
 // when it is successfully started.
 const char kSignalParentSwitchName[] = "signal-parent";
 
+// Command line switch used to enable VP9 encoding.
+const char kEnableVp9SwitchName[] = "enable-vp9";
+
 // Value used for --host-config option to indicate that the path must be read
 // from stdin.
 const char kStdinConfigPath[] = "-";
@@ -287,6 +290,7 @@ class HostProcess
   std::string serialized_config_;
   std::string host_owner_;
   bool use_service_account_;
+  bool enable_vp9_;
 
   scoped_ptr<policy_hack::PolicyWatcher> policy_watcher_;
   std::string host_domain_;
@@ -331,6 +335,8 @@ HostProcess::HostProcess(scoped_ptr<ChromotingHostContext> context,
     : context_(context.Pass()),
       state_(HOST_INITIALIZING),
       use_service_account_(false),
+      enable_vp9_(
+          CommandLine::ForCurrentProcess()->HasSwitch(kEnableVp9SwitchName)),
       host_username_match_required_(false),
       allow_nat_traversal_(true),
       allow_relay_(true),
@@ -816,6 +822,10 @@ bool HostProcess::ApplyConfig(scoped_ptr<JsonHostConfig> config) {
     host_owner_ = xmpp_server_config_.username;
     use_service_account_ = false;
   }
+
+  // If the enable VP9 option is unspecified, or false, then VP9 is not offered.

[Jamie, 2014/06/17 17:35:48]

It actually falls back on the command-line, I think. Is that the right
semantics? I would expect the command-line to override anything set in the
config file.

[Sergey Ulanov, 2014/06/17 17:37:58]

I think this should also mention the optional CL flag.

+  config->GetBoolean(kEnableVp9ConfigPath, &enable_vp9_);

[Sergey Ulanov, 2014/06/17 17:37:59]

Shouldn't command-line option override the flag in the config?
I would prefer initializing enable_vp9_ to false in the constructor and then
call CommandLine::ForCurrentProcess()->HasSwitch() here

[Wez, 2014/06/17 17:58:23]

Done.

+
   return true;
 }
 
@@ -1190,6 +1200,14 @@ void HostProcess::StartHost() {
       context_->network_task_runner(),
       context_->ui_task_runner()));
 
+  // Enable VP9 if configured via the host config.

[Jamie, 2014/06/17 17:35:48]

It can also be configured on the command-line. I think I would just remove the
detail from the command. Maybe even just remove the comment.

[Wez, 2014/06/17 17:58:23]

Done.

+  if (enable_vp9_) {
+    scoped_ptr<protocol::CandidateSessionConfig> config =
+        host_->protocol_config()->Clone();
+    config->EnableVideoCodec(protocol::ChannelConfig::CODEC_VP9);
+    host_->set_protocol_config(config.Pass());
+  }
+
   // TODO(simonmorris): Get the maximum session duration from a policy.
 #if defined(OS_LINUX)
   host_->SetMaximumSessionDuration(base::TimeDelta::FromHours(20));