Fix cpplint errors in p2p/

Bug: webrtc:5273
Change-Id: Ida3c2ca1bbb611026f34d7144db9ec24840bf7fb
Reviewed-on: https://webrtc-review.googlesource.com/26444
Commit-Queue: Steve Anton <steveanton@webrtc.org>
Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#21133}
diff --git a/p2p/base/stunrequest.h b/p2p/base/stunrequest.h
index 7bb0466..99173af 100644
--- a/p2p/base/stunrequest.h
+++ b/p2p/base/stunrequest.h
@@ -32,7 +32,7 @@
 // response or determine that the request has timed out.
 class StunRequestManager {
  public:
-  StunRequestManager(rtc::Thread* thread);
+  explicit StunRequestManager(rtc::Thread* thread);
   ~StunRequestManager();
 
   // Starts sending the given request (perhaps after a delay).
@@ -83,7 +83,7 @@
 class StunRequest : public rtc::MessageHandler {
  public:
   StunRequest();
-  StunRequest(StunMessage* request);
+  explicit StunRequest(StunMessage* request);
   ~StunRequest() override;
 
   // Causes our wrapped StunMessage to be Prepared