[Hotword] Add error message display back in. Add error messages for NaCl. Add metrics for errors.

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 c7418c124263f06c2449a0bbd94e8d97eaf9eb68..188783c005d9323462f854ed620b044a89d24279 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -7677,6 +7677,7 @@ Therefore, the affected-histogram name has to have at least one dot in it.
 </histogram>
 
 <histogram name="Hotword.AudioLoggingEnabled" enum="BooleanEnabled">
+  <owner>rlp@chromium.org</owner>
   <summary>
     The state of the hotword audio logging preference. This value is emitted
     each time the hotword availability is requested by the extension if the user
@@ -7703,6 +7704,15 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   </summary>
 </histogram>
 
+<histogram name="Hotword.HotwordError" enum="HotwordError">
+  <owner>rlp@chromium.org</owner>
+  <summary>
+    Errors reported by the hotword service when determining if hotwording is
+    available. Non-errors are also reported so that errors can be seen as a
+    percentage of total requests.
+  </summary>
+</histogram>
+
 <histogram name="HttpCache.EntryLockWait" units="milliseconds">
   <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
   <summary>
@@ -35901,6 +35911,13 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   <int value="3" label="Disabled"/>
 </enum>
 
+<enum name="HotwordError" type="int">
+  <int value="0" label="No error"/>
+  <int value="1" label="Generic error"/>
+  <int value="2" label="NaCl error"/>
+  <int value="3" label="Microphone error"/>
+</enum>
+
 <enum name="HotwordPrefState" type="int">
   <int value="0" label="Preference not set"/>
   <int value="1" label="Hotwording enabled"/>