Delete unused methods of the VideoProcessing class. And fix a typo.

webrtc/modules/video_processing/video_processing.gypi

Index: webrtc/modules/video_processing/video_processing.gypi
diff --git a/webrtc/modules/video_processing/video_processing.gypi b/webrtc/modules/video_processing/video_processing.gypi
index 5bf0ea36c36a39fdabc1bf45a6016ec14bc1fc3c..429d74ccb81453b3be9fc675625325ae46d84905 100644
--- a/webrtc/modules/video_processing/video_processing.gypi
+++ b/webrtc/modules/video_processing/video_processing.gypi
@@ -20,12 +20,8 @@
       'sources': [
         'include/video_processing.h',
         'include/video_processing_defines.h',
-        'brightness_detection.cc',
-        'brightness_detection.h',
         'content_analysis.cc',
         'content_analysis.h',
-        'deflickering.cc',
-        'deflickering.h',
         'frame_preprocessor.cc',
         'frame_preprocessor.h',
         'spatial_resampler.cc',