Add histogram definitions for Chrome OS crouton statistics

tools/metrics/histograms/histograms.xml

Index: tools/metrics/histograms/histograms.xml
diff --git a/tools/metrics/histograms/histograms.xml b/tools/metrics/histograms/histograms.xml
index b2c49278b3d401d6689c3be9884f9b47feaa3a35..aecb49ff43cbdf0620df42804e08c0d92f773ec0 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -43940,6 +43940,16 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="Platform.Crouton.Started" enum="Platform.Crouton.Started">
+  <owner>drinkcat@chromium.org</owner>
+  <summary>
+    Detects presence of /run/crouton, indicating that crouton has been started
+    since the previous boot. Value 0/&quot;Total count&quot; is reported on
+    boot, 1/&quot;Started&quot; is reported after the file presence is detected
+    (checked periodically).
+  </summary>
+</histogram>
+
 <histogram name="Platform.CumulativeCpuTime" units="seconds">
   <owner>semenzato@chromium.org</owner>
   <owner>bsimonnet@chromium.org</owner>
@@ -96955,6 +96965,11 @@ value.
   <int value="2" label="Error"/>
 </enum>
 
+<enum name="Platform.Crouton.Started" type="int">
+  <int value="0" label="Total count"/>
+  <int value="1" label="Started"/>
+</enum>
+
 <enum name="PlatformFileError" type="int">
   <int value="0" label="OK"/>
   <int value="1" label="FAILED"/>