Delay the expiration of Media Router extension histograms

The extension is being deprecated soon so the histograms should no
longer be necessary by this time next year, but we'll keep them around
until then in case we need them during the turndown.

Bug: 1160947
Change-Id: Iebc7f139b22dd4759c626bb9692b752e42f1e6b5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2637959Reviewed-by: Steven Holte <holte@chromium.org>
Commit-Queue: Takumi Fujimoto <takumif@chromium.org>
Cr-Commit-Position: refs/heads/master@{#845462}

tools/metrics/histograms/histograms_xml/media/histograms.xml

@@ -4752,7 +4752,7 @@ reviews. Googlers can read more about this at go/gwsq-gerrit.
 </histogram>
 
 <histogram name="MediaRouter.Cloud.PrefAtDialogOpen" enum="BooleanEnabled"
-    expires_after="2021-02-01">
+    expires_after="2022-02-01">
   <owner>takumif@chromium.org</owner>
   <owner>openscreen-eng@google.com</owner>
   <summary>
@@ -4762,7 +4762,7 @@ reviews. Googlers can read more about this at go/gwsq-gerrit.
 </histogram>
 
 <histogram name="MediaRouter.Cloud.PrefAtInit" enum="BooleanEnabled"
-    expires_after="2021-02-01">
+    expires_after="2022-02-01">
   <owner>takumif@chromium.org</owner>
   <owner>openscreen-eng@google.com</owner>
   <summary>
@@ -4957,7 +4957,7 @@ reviews. Googlers can read more about this at go/gwsq-gerrit.
 </histogram>
 
 <histogram name="MediaRouter.Provider.Version" enum="MediaRouteProviderVersion"
-    expires_after="2021-02-01">
+    expires_after="2022-02-01">
   <owner>mfoltz@chromium.org</owner>
   <owner>openscreen-eng@google.com</owner>
   <summary>
@@ -4967,7 +4967,7 @@ reviews. Googlers can read more about this at go/gwsq-gerrit.
 </histogram>
 
 <histogram name="MediaRouter.Provider.WakeReason"
-    enum="MediaRouteProviderWakeReason" expires_after="2021-05-16">
+    enum="MediaRouteProviderWakeReason" expires_after="2022-02-01">
   <owner>mfoltz@chromium.org</owner>
   <owner>openscreen-eng@google.com</owner>
   <summary>
@@ -4976,7 +4976,7 @@ reviews. Googlers can read more about this at go/gwsq-gerrit.
 </histogram>
 
 <histogram name="MediaRouter.Provider.Wakeup" enum="MediaRouteProviderWakeup"
-    expires_after="2021-02-01">
+    expires_after="2022-02-01">
   <owner>mfoltz@chromium.org</owner>
   <owner>openscreen-eng@google.com</owner>
   <summary>