UMA stats for MTP file system in Chrome OS Files.app.

chrome/browser/chromeos/file_manager/volume_manager.cc

Index: chrome/browser/chromeos/file_manager/volume_manager.cc
diff --git a/chrome/browser/chromeos/file_manager/volume_manager.cc b/chrome/browser/chromeos/file_manager/volume_manager.cc
index 619b9b12e4cee1256b5043bd001c0627ce15a642..862967f0717adb11843c64a6229fdad48e104248 100644
--- a/chrome/browser/chromeos/file_manager/volume_manager.cc
+++ b/chrome/browser/chromeos/file_manager/volume_manager.cc
@@ -11,6 +11,7 @@
 #include "base/files/file_path.h"
 #include "base/logging.h"
 #include "base/memory/singleton.h"
+#include "base/metrics/histogram.h"
 #include "base/prefs/pref_service.h"
 #include "base/strings/utf_string_conversions.h"
 #include "chrome/browser/chromeos/drive/drive_integration_service.h"
@@ -728,6 +729,8 @@ void VolumeManager::OnRemovableStorageAttached(
           base::Unretained(MTPDeviceMapService::GetInstance()),
           info.location(), fsid));
 
+  UMA_HISTOGRAM_COUNTS("FileBrowser.MTPMount", 1);

[Ilya Sherman, 2014/05/01 21:15:24]

You're currently allocating space for 50 buckets, and only using one of them. 
Please only allocate as many buckets as you need.

[kinaba, 2014/05/08 04:15:41]

Done.

+
   VolumeInfo volume_info;
   volume_info.type = VOLUME_TYPE_MTP;
   volume_info.mount_path = path;