Add host-side rate-limiting to desktop resize events.

remoting/host/client_session.cc

Index: remoting/host/client_session.cc
diff --git a/remoting/host/client_session.cc b/remoting/host/client_session.cc
index 2f17ce854442ff00094337bff4ef41cca2e0ac7e..62aa056a455c6a72c7528d39104076764d584382 100644
--- a/remoting/host/client_session.cc
+++ b/remoting/host/client_session.cc
@@ -31,6 +31,10 @@
 // Default DPI to assume for old clients that use notifyClientDimensions.
 const int kDefaultDPI = 96;
 
+// All DesktopEnvironment implementations rate-limit desktop resize requests,
+// so this Capability is added automatically.
+const char kRateLimitResizeRequests[] = "rateLimitResizeRequests";
+
 namespace remoting {
 
 ClientSession::ClientSession(
@@ -211,6 +215,7 @@ void ClientSession::OnConnectionAuthenticated(
   }
 
   host_capabilities_ = desktop_environment_->GetCapabilities();
+  host_capabilities_ = host_capabilities_ + " " + kRateLimitResizeRequests;

[Jamie, 2013/06/04 01:27:49]

Is this an acceptable way of getting the capability registered (as opposed to
doing so in every DesktopEnvironment)?

[alexeypa (please no reviews), 2013/06/04 17:07:37]

No, I don't think we should do it this way. I think each desktop environment
should explicitly specify this capability. I realize that it means more code has
to be written but there are two compelling reasons to do it:

1. It is very easy to miss that all DE instances should implement rate-limiting
unless rate limiting is implemented in ClientSession. (which is probably not a
good idea too).
2. There are at least two kinds DE that don't implement rate limiting even with
this CL applied: It2MeDesktopEnvironment and IpcDesktopEnvironment. The latter
also invokes different code for curtained (RdpDesktopSession) and not curtained
(Me2meDesktopEnvironment) sessions.

[Jamie, 2013/06/04 21:18:03]

Done. However, see my comments below.
Rate-limiting is implemented by a platform independent class, so any desktop
environment that supports resize gets it automatically. If a desktop environment
doesn't support resize, then we end up reporting that it rate-limits resize
requests, which is misleading, but not harmful afaict.
I believe that IpcDesktopEnvironment does implement rate-limiting, as long as
the underlying DE does. In any case, with the change as I've implemented it now,
it still reports that it implements rate-limiting without consulting the
underlying DE, as that would require extending the IPC, which is overkill imo.

 
   // Ignore protocol::Capabilities messages from the client if it does not
   // support any capabilities.