Enable cpplint for webrtc/examples and fix all uncovered cpplint errors.

webrtc/examples/peerconnection/client/peer_connection_client.h

Index: webrtc/examples/peerconnection/client/peer_connection_client.h
diff --git a/webrtc/examples/peerconnection/client/peer_connection_client.h b/webrtc/examples/peerconnection/client/peer_connection_client.h
index 5b5787bc14ecb0ef721e7218ad4421a56ed78ba7..b7abfdfe18e80684efb77c0a419c7f6e484fe3af 100644
--- a/webrtc/examples/peerconnection/client/peer_connection_client.h
+++ b/webrtc/examples/peerconnection/client/peer_connection_client.h
@@ -8,8 +8,8 @@
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
-#ifndef PEERCONNECTION_SAMPLES_CLIENT_PEER_CONNECTION_CLIENT_H_
-#define PEERCONNECTION_SAMPLES_CLIENT_PEER_CONNECTION_CLIENT_H_
+#ifndef WEBRTC_EXAMPLES_PEERCONNECTION_CLIENT_PEER_CONNECTION_CLIENT_H_
+#define WEBRTC_EXAMPLES_PEERCONNECTION_CLIENT_PEER_CONNECTION_CLIENT_H_
 #pragma once
 
 #include <map>
@@ -120,4 +120,4 @@ class PeerConnectionClient : public sigslot::has_slots<>,
   int my_id_;
 };
 
-#endif  // PEERCONNECTION_SAMPLES_CLIENT_PEER_CONNECTION_CLIENT_H_
+#endif  // WEBRTC_EXAMPLES_PEERCONNECTION_CLIENT_PEER_CONNECTION_CLIENT_H_