[omnibox metrics] Change tab-switch from bools to enums of bools

Also added enum for "tab switch offered". This allows UMA to treat
the data (0,1) as entities, not quantities.

Bug: 854714
Change-Id: I891aa38603c741070013a6cb06cc52df2bce14cb
Reviewed-on: https://chromium-review.googlesource.com/1247028
Commit-Queue: Kevin Bailey <krb@chromium.org>
Reviewed-by: Mark Pearson <mpearson@chromium.org>
Cr-Commit-Position: refs/heads/master@{#595094}

tools/metrics/histograms/enums.xml

@@ -4756,6 +4756,11 @@ uploading your change for review.  These are checked by presubmit scripts.
   <int value="1" label="Connection's visitor is a nullptr"/>
 </enum>
 
+<enum name="BooleanOffered">
+  <int value="0" label="Not offered"/>
+  <int value="1" label="Offered"/>
+</enum>
+
 <enum name="BooleanOnBattery">
   <int value="0" label="Not on battery"/>
   <int value="1" label="On Battery"/>
@@ -4935,7 +4940,7 @@ uploading your change for review.  These are checked by presubmit scripts.
 </enum>
 
 <enum name="BooleanSelected">
-  <int value="0" label="No selection"/>
+  <int value="0" label="Not selected"/>
   <int value="1" label="Selected"/>
 </enum>
 

tools/metrics/histograms/histograms.xml

@@ -68386,7 +68386,7 @@ uploading your change for review.
   </summary>
 </histogram>
 
-<histogram name="Omnibox.SuggestionUsed.OfferedTabMatch" units="Boolean">
+<histogram name="Omnibox.SuggestionUsed.OfferedTabMatch" enum="BooleanOffered">
   <owner>krb@chromium.org</owner>
   <owner>jdonnelly@chromium.org</owner>
   <summary>
@@ -68518,7 +68518,8 @@ uploading your change for review.
   </summary>
 </histogram>
 
-<histogram name="Omnibox.SuggestionUsed.SelectedTabMatch" units="Boolean">
+<histogram name="Omnibox.SuggestionUsed.SelectedTabMatch"
+    enum="BooleanSelected">
   <owner>krb@chromium.org</owner>
   <owner>jdonnelly@chromium.org</owner>
   <summary>