Enable cpplint in pc/

Enable cpplint check in the PRESUBMIT for pc/ and fix all existing
warnings.

Bug: webrtc:5583
Change-Id: If39994692ab6f6f3c83c74f23850f02fdfe810e8
Reviewed-on: https://webrtc-review.googlesource.com/16540
Commit-Queue: Steve Anton <steveanton@webrtc.org>
Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#20482}

pc/peerconnectionfactory.h

diff --git a/pc/peerconnectionfactory.h b/pc/peerconnectionfactory.h
index f5faecc..398221f 100644
--- a/pc/peerconnectionfactory.h
+++ b/pc/peerconnectionfactory.h
@@ -49,7 +49,7 @@
       std::unique_ptr<rtc::RTCCertificateGeneratorInterface> cert_generator,
       PeerConnectionObserver* observer) override;
 
-  virtual rtc::scoped_refptr<PeerConnectionInterface> CreatePeerConnection(
+  rtc::scoped_refptr<PeerConnectionInterface> CreatePeerConnection(
       const PeerConnectionInterface::RTCConfiguration& configuration,
       std::unique_ptr<cricket::PortAllocator> allocator,
       std::unique_ptr<rtc::RTCCertificateGeneratorInterface> cert_generator,
@@ -60,13 +60,13 @@
   rtc::scoped_refptr<MediaStreamInterface>
       CreateLocalMediaStream(const std::string& label) override;
 
-  virtual rtc::scoped_refptr<AudioSourceInterface> CreateAudioSource(
+  rtc::scoped_refptr<AudioSourceInterface> CreateAudioSource(
       const cricket::AudioOptions& options) override;
   // Deprecated, use version without constraints.
   rtc::scoped_refptr<AudioSourceInterface> CreateAudioSource(
       const MediaConstraintsInterface* constraints) override;
 
-  virtual rtc::scoped_refptr<VideoTrackSourceInterface> CreateVideoSource(
+  rtc::scoped_refptr<VideoTrackSourceInterface> CreateVideoSource(
       std::unique_ptr<cricket::VideoCapturer> capturer) override;
   // This version supports filtering on width, height and frame rate.
   // For the "constraints=null" case, use the version without constraints.