[Chromoting] Use HostExperimentSessionPlugin in host

remoting/protocol/fake_session.h

Index: remoting/protocol/fake_session.h
diff --git a/remoting/protocol/fake_session.h b/remoting/protocol/fake_session.h
index 7d31c9c064fc61f63987cd9c47e010a512cf90b6..6100136ff7822b5eee4324f3e103b6c2f383e9d7 100644
--- a/remoting/protocol/fake_session.h
+++ b/remoting/protocol/fake_session.h
@@ -5,6 +5,7 @@
 #ifndef REMOTING_PROTOCOL_FAKE_SESSION_H_
 #define REMOTING_PROTOCOL_FAKE_SESSION_H_
 
+#include <deque>
 #include <map>
 #include <memory>
 #include <string>
@@ -14,6 +15,7 @@
 #include "base/memory/weak_ptr.h"
 #include "base/time/time.h"
 #include "remoting/protocol/fake_stream_socket.h"
+#include "remoting/protocol/jingle_messages.h"
 #include "remoting/protocol/session.h"
 #include "remoting/protocol/transport.h"
 
@@ -40,6 +42,11 @@ class FakeSession : public Session {
     signaling_delay_ = signaling_delay;
   }
 
+  // Adds an |attachment| to |round|, which will be sent to plugins added by
+  // AddPlugin() function.
+  void SetAttachment(size_t round,

[Sergey Ulanov, 2017/01/09 23:00:26]

int would be more appropriate here than size_t, but I think it would be better
to replace this function with 
SetAttachments(std::vector<std::unique_ptr<buzz::XmlElement>> attachments)
to set all attachments at once.

[Hzj_jie, 2017/01/10 02:31:10]

Then it would be complex if the FakeSession has been sent through several
components, and each component needs to set its own SessionPlugin and
attachments.

+                     std::unique_ptr<buzz::XmlElement> attachment);
+
   // Session interface.
   void SetEventHandler(EventHandler* event_handler) override;
   ErrorCode error() override;
@@ -70,6 +77,8 @@ class FakeSession : public Session {
   base::WeakPtr<FakeSession> peer_;
   base::TimeDelta signaling_delay_;
 
+  std::deque<JingleMessage> attachments_;

[Sergey Ulanov, 2017/01/09 23:00:26]

I'd prefer to avoid using std::deque<> anywhere in new code. Depending on impl
it can be rather inefficient, see crbug.com/674287 . This is a test code, so it
doesn't make much difference here, but for consistency I would prefer to avoid
it in test code as well. This class needs only emplace_back() and operator[], so
you could use std::vector<> instead.

[Hzj_jie, 2017/01/10 02:31:10]

It's a little bit complex, and relates to the implementation of vector. Since
vector creates a new array, and copy all the elements from old one when the old
array is full. If we actively provide a destructor, vector will use
copy-assignment or move-constructor, so the destructor can be correctly
involved. But copy-assignment is disabled because of the unique_ptr variables,
and we do not define a move-constructor, so it will trigger a build break. A
simpler sample is @ http://cpp.sh/6hvul.

List does not provide a random access (operator[] here), so it won't support the
scenario.

Deque does not need to move the internal array, so it does not require
copy-assignment or move-contructor.

So we can do one of the following two,
1. Change JingleMessage to remove the destructor, which is not really necessary,
or provide a move constructor by simply add JingleMessage(JingleMessage&&) =
default. Then it should be able to work with vector.
2. Use deque, since it's in test code, which does not really impact the
production performance.

[Sergey Ulanov, 2017/01/23 00:51:35]

I don't think you need to store JingleMessages here. Only the attachments field
is used, so this can be std::vector<std::unique_ptr<buzz::XmlElement>> .

[Hzj_jie, 2017/02/08 01:56:29]

Done.

+
   base::WeakPtrFactory<FakeSession> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(FakeSession);