Add UMA to count directory-changed events by RootType.

tools/metrics/histograms/enums.xml

Index: tools/metrics/histograms/enums.xml
diff --git a/tools/metrics/histograms/enums.xml b/tools/metrics/histograms/enums.xml
index a05ea63c6e53137b4682ae4e2cf9072cad9dcdaf..909969ef162b3d8ab0bea1ad568651c7404b1056 100644
--- a/tools/metrics/histograms/enums.xml
+++ b/tools/metrics/histograms/enums.xml
@@ -15756,6 +15756,22 @@ uploading your change for review.  These are checked by presubmit scripts.
   <int value="1" label="Space key"/>
 </enum>
 
+<enum name="FileManagerRootType" type="int">
+  <int value="0" label="DOWNLOADS"/>
+  <int value="1" label="ARCHIVE"/>
+  <int value="2" label="REMOVABLE"/>
+  <int value="3" label="DRIVE"/>
+  <int value="4" label="TEAM_DRIVES_GRAND_ROOT"/>
+  <int value="5" label="TEAM_DRIVE"/>
+  <int value="6" label="MTP"/>
+  <int value="7" label="PROVIDED"/>
+  <int value="8" label="DRIVE_OTHER"/>
+  <int value="9" label="DRIVE_OFFLINE"/>
+  <int value="10" label="DRIVE_SHARED_WITH_ME"/>
+  <int value="11" label="DRIVE_RECENT"/>
+  <int value="12" label="MEDIA_VIEW"/>
+</enum>
+
 <enum name="FileManagerVolumeType" type="int">
   <int value="0" label="Google Drive"/>
   <int value="1" label="Download Folder"/>