Extend the expiry date of OfflineIndicator.CTR

Bug: 967486
Change-Id: Iea0b436f94bb7dbfbbde8a97d14e7219f385f2fa
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1635879Reviewed-by: Peter Williamson <petewil@chromium.org>
Reviewed-by: Mark Pearson <mpearson@chromium.org>
Commit-Queue: Jian Li <jianli@chromium.org>
Cr-Commit-Position: refs/heads/master@{#664447}

tools/metrics/histograms/histograms.xml

@@ -81733,7 +81733,7 @@ uploading your change for review.
 </histogram>
 
 <histogram name="OfflineIndicator.CTR" enum="OfflineIndicatorCTREvent"
-    expires_after="2019-06-30">
+    expires_after="2019-11-30">
   <owner>dimich@chromium.org</owner>
   <owner>jianli@chromium.org</owner>
   <summary>