metrics: mark bubble histograms as obsolete

These have not been looked at for a long time, and as of r722561 are
not gathered any more.

Bug: 496955
Change-Id: I4457fb6bafad9324b99017ae1a344183bd1e099a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1954257
Commit-Queue: Elly Fong-Jones <ellyjones@chromium.org>
Reviewed-by: Ilya Sherman <isherman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#723482}

tools/metrics/histograms/histograms.xml

@@ -20475,11 +20475,17 @@ uploading your change for review.
 </histogram>
 
 <histogram name="Bubbles.Close.Accepted" enum="BubbleType" expires_after="M77">
+  <obsolete>
+    No longer used; generating code removed in M81.
+  </obsolete>
   <owner>hcarmona@chromium.org</owner>
   <summary>An open bubble was closed because the user accepted it.</summary>
 </histogram>
 
 <histogram name="Bubbles.Close.Canceled" enum="BubbleType" expires_after="M78">
+  <obsolete>
+    No longer used; generating code removed in M81.
+  </obsolete>
   <owner>hcarmona@chromium.org</owner>
   <summary>
     An open bubble was closed because the user didn't accept it.
@@ -20487,21 +20493,33 @@ uploading your change for review.
 </histogram>
 
 <histogram name="Bubbles.Close.FocusLost" enum="BubbleType" expires_after="M77">
+  <obsolete>
+    No longer used; generating code removed in M81.
+  </obsolete>
   <owner>hcarmona@chromium.org</owner>
   <summary>An open bubble was closed because of a focus change.</summary>
 </histogram>
 
 <histogram name="Bubbles.Close.Forced" enum="BubbleType" expires_after="M77">
+  <obsolete>
+    No longer used; generating code removed in M81.
+  </obsolete>
   <owner>hcarmona@chromium.org</owner>
   <summary>An open bubble was forced to close.</summary>
 </histogram>
 
 <histogram name="Bubbles.Close.FrameDestroyed" enum="BubbleType">
+  <obsolete>
+    No longer used; generating code removed in M81.
+  </obsolete>
   <owner>hcarmona@chromium.org</owner>
   <summary>An open bubble was dismissed because a frame was destroyed.</summary>
 </histogram>
 
 <histogram name="Bubbles.Close.FullscreenToggled" enum="BubbleType">
+  <obsolete>
+    No longer used; generating code removed in M81.
+  </obsolete>
   <owner>hcarmona@chromium.org</owner>
   <summary>
     An open bubble was dismissed because fullscreen was toggled.
@@ -20509,6 +20527,9 @@ uploading your change for review.
 </histogram>
 
 <histogram name="Bubbles.Close.Navigated" enum="BubbleType" expires_after="M78">
+  <obsolete>
+    No longer used; generating code removed in M81.
+  </obsolete>
   <owner>hcarmona@chromium.org</owner>
   <summary>
     An open bubble was dismissed because the page was navigated.
@@ -20517,17 +20538,26 @@ uploading your change for review.
 
 <histogram name="Bubbles.Close.TabDetached" enum="BubbleType"
     expires_after="M77">
+  <obsolete>
+    No longer used; generating code removed in M81.
+  </obsolete>
   <owner>hcarmona@chromium.org</owner>
   <summary>An open bubble was closed because a tab was detached.</summary>
 </histogram>
 
 <histogram name="Bubbles.Close.TabSwitched" enum="BubbleType"
     expires_after="M77">
+  <obsolete>
+    No longer used; generating code removed in M81.
+  </obsolete>
   <owner>hcarmona@chromium.org</owner>
   <summary>An open bubble was closed because a tab was switched.</summary>
 </histogram>
 
 <histogram name="Bubbles.Close.UserDismissed" enum="BubbleType">
+  <obsolete>
+    No longer used; generating code removed in M81.
+  </obsolete>
   <owner>hcarmona@chromium.org</owner>
   <summary>
     An open bubble was dismissed by the user without making a decission.
@@ -20535,6 +20565,9 @@ uploading your change for review.
 </histogram>
 
 <histogram name="Bubbles.DisplayTime.All" units="ms" expires_after="M77">
+  <obsolete>
+    No longer used; generating code removed in M81.
+  </obsolete>
   <owner>hcarmona@chromium.org</owner>
   <summary>
     Log the amount of time any bubble was visible. Only bubbles that are shown
@@ -20543,6 +20576,9 @@ uploading your change for review.
 </histogram>
 
 <histogram name="Bubbles.NeverShown" enum="BubbleType">
+  <obsolete>
+    No longer used; generating code removed in M81.
+  </obsolete>
   <owner>hcarmona@chromium.org</owner>
   <summary>A bubble was given to the bubble manager but not shown.</summary>
 </histogram>