Remove mutable from rtc::CriticalSection members.

rtc::CriticalSection is now lockable from const methods and no longer
need to remain mutable.

BUG=
R=tommi@webrtc.org

Review URL: https://codereview.webrtc.org/1613643004

Cr-Commit-Position: refs/heads/master@{#11367}
diff --git a/webrtc/modules/video_coding/codecs/vp9/vp9_frame_buffer_pool.h b/webrtc/modules/video_coding/codecs/vp9/vp9_frame_buffer_pool.h
index 97ed41a..8551689 100644
--- a/webrtc/modules/video_coding/codecs/vp9/vp9_frame_buffer_pool.h
+++ b/webrtc/modules/video_coding/codecs/vp9/vp9_frame_buffer_pool.h
@@ -9,8 +9,8 @@
  *
  */
 
-#ifndef WEBRTC_MODULES_VIDEO_CODING_CODECS_VP9_FRAME_BUFFER_POOL_H_
-#define WEBRTC_MODULES_VIDEO_CODING_CODECS_VP9_FRAME_BUFFER_POOL_H_
+#ifndef WEBRTC_MODULES_VIDEO_CODING_CODECS_VP9_VP9_FRAME_BUFFER_POOL_H_
+#define WEBRTC_MODULES_VIDEO_CODING_CODECS_VP9_VP9_FRAME_BUFFER_POOL_H_
 
 #include <vector>
 
@@ -103,7 +103,7 @@
 
  private:
   // Protects |allocated_buffers_|.
-  mutable rtc::CriticalSection buffers_lock_;
+  rtc::CriticalSection buffers_lock_;
   // All buffers, in use or ready to be recycled.
   std::vector<rtc::scoped_refptr<Vp9FrameBuffer>> allocated_buffers_
       GUARDED_BY(buffers_lock_);
@@ -114,4 +114,4 @@
 
 }  // namespace webrtc
 
-#endif  // WEBRTC_MODULES_VIDEO_CODING_CODECS_VP9_FRAME_BUFFER_POOL_H_
+#endif  // WEBRTC_MODULES_VIDEO_CODING_CODECS_VP9_VP9_FRAME_BUFFER_POOL_H_
diff --git a/webrtc/modules/video_coding/generic_encoder.h b/webrtc/modules/video_coding/generic_encoder.h
index f739edb..da7297f 100644
--- a/webrtc/modules/video_coding/generic_encoder.h
+++ b/webrtc/modules/video_coding/generic_encoder.h
@@ -138,7 +138,7 @@
   VideoEncoderRateObserver* const rate_observer_;
   VCMEncodedFrameCallback* const vcm_encoded_frame_callback_;
   const bool internal_source_;
-  mutable rtc::CriticalSection params_lock_;
+  rtc::CriticalSection params_lock_;
   EncoderParameters encoder_params_ GUARDED_BY(params_lock_);
   VideoRotation rotation_;
   bool is_screenshare_;
diff --git a/webrtc/modules/video_coding/video_coding_impl.h b/webrtc/modules/video_coding/video_coding_impl.h
index 1ed96e1..7373325 100644
--- a/webrtc/modules/video_coding/video_coding_impl.h
+++ b/webrtc/modules/video_coding/video_coding_impl.h
@@ -104,7 +104,7 @@
   Clock* const clock_;
 
   rtc::scoped_ptr<CriticalSectionWrapper> process_crit_sect_;
-  mutable rtc::CriticalSection encoder_crit_;
+  rtc::CriticalSection encoder_crit_;
   VCMGenericEncoder* _encoder;
   VCMEncodedFrameCallback _encodedFrameCallback GUARDED_BY(encoder_crit_);
   media_optimization::MediaOptimization _mediaOpt;