Change name of files and class in agc/histogram* in order to avoid file-name clash.

webrtc/tools/agc/activity_metric.cc

Index: webrtc/tools/agc/activity_metric.cc
diff --git a/webrtc/tools/agc/activity_metric.cc b/webrtc/tools/agc/activity_metric.cc
index 6c1f756ec58bf30ecc7d0bc564f6e3fc73868695..c3b46cae7afae8c781bb93e2c426d552795a4490 100644
--- a/webrtc/tools/agc/activity_metric.cc
+++ b/webrtc/tools/agc/activity_metric.cc
@@ -19,7 +19,7 @@
 #include "gflags/gflags.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #include "webrtc/modules/audio_processing/agc/agc.h"
-#include "webrtc/modules/audio_processing/agc/histogram.h"
+#include "webrtc/modules/audio_processing/agc/loudness_histogram.h"
 #include "webrtc/modules/audio_processing/agc/utility.h"
 #include "webrtc/modules/audio_processing/vad/vad_audio_proc.h"
 #include "webrtc/modules/audio_processing/vad/common.h"
@@ -75,7 +75,7 @@ class AgcStat {
   AgcStat()
       : video_index_(0),
         activity_threshold_(kDefaultActivityThreshold),
-        audio_content_(Histogram::Create(kAgcAnalWindowSamples)),
+        audio_content_(LoudnessHistogram::Create(kAgcAnalWindowSamples)),
         audio_processing_(new VadAudioProc()),
         vad_(new PitchBasedVad()),
         standalone_vad_(StandaloneVad::Create()),
@@ -155,7 +155,7 @@ class AgcStat {
   int video_index_;
   double activity_threshold_;
   double video_vad_[kMaxNumFrames];
-  std::unique_ptr<Histogram> audio_content_;
+  std::unique_ptr<LoudnessHistogram> audio_content_;
   std::unique_ptr<VadAudioProc> audio_processing_;
   std::unique_ptr<PitchBasedVad> vad_;
   std::unique_ptr<StandaloneVad> standalone_vad_;