[Chromoting] Use SessionOptions instead of SetPreferredVideoCodec

After cl 776197, SessionOptions can be referred by protocol/ and codec/, so we
can use it to forward the session options instead of using pure string for
video codec selection.

This change should have no behavior impact.

Bug: chromium:781432
Change-Id: Id7b87d460a4789dead75806f6f33d731cf8ddada
Reviewed-on: https://chromium-review.googlesource.com/777776
Commit-Queue: Zijie He <[email protected]>
Reviewed-by: Lambros Lambrou <[email protected]>
Cr-Commit-Position: refs/heads/master@{#517908}
diff --git a/remoting/base/session_options.cc b/remoting/base/session_options.cc
index e39c436f9..b152274 100644
--- a/remoting/base/session_options.cc
+++ b/remoting/base/session_options.cc
@@ -33,12 +33,19 @@
 }  // namespace
 
 SessionOptions::SessionOptions() = default;
-SessionOptions::~SessionOptions() = default;
+SessionOptions::SessionOptions(const SessionOptions& other) = default;
+SessionOptions::SessionOptions(SessionOptions&& other) = default;
 
 SessionOptions::SessionOptions(const std::string& parameter) {
   Import(parameter);
 }
 
+SessionOptions::~SessionOptions() = default;
+
+SessionOptions& SessionOptions::operator=(
+    const SessionOptions& other) = default;
+SessionOptions& SessionOptions::operator=(SessionOptions&& other) = default;
+
 void SessionOptions::Append(const std::string& key,
                                 const std::string& value) {
   DCHECK(KeyIsValid(key));