[AW] Extend NonEmbeddedMetrics* histograms by 6 months

This histograms are still relevant and useful to mentor the service
performance and to make sure it's running as expected. Thus, I am
extending it by 6 months per the public docs:
https://chromium.googlesource.com/chromium/src/+/master/tools/metrics/histograms/README.md#how-to-choose-expiry-for-histograms

Fixed: 1156193
Test: N/A
Change-Id: I1a3fbe5dd39b2eefc8576acce59296cf87ed36fa
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2637707
Commit-Queue: Robert Kaplow <rkaplow@chromium.org>
Reviewed-by: Robert Kaplow <rkaplow@chromium.org>
Auto-Submit: Hazem Ashmawy <hazems@chromium.org>
Cr-Commit-Position: refs/heads/master@{#845163}

tools/metrics/histograms/histograms_xml/android/histograms.xml

@@ -2617,7 +2617,7 @@ reviews. Googlers can read more about this at go/gwsq-gerrit.
 </histogram>
 
 <histogram name="Android.WebView.NonEmbeddedMetrics.HistogramRecordAge"
-    units="minutes" expires_after="2021-01-20">
+    units="minutes" expires_after="2021-07-20">
   <owner>hazems@chromium.org</owner>
   <owner>ntfschr@chromium.org</owner>
   <owner>src/android_webview/OWNERS</owner>
@@ -2631,7 +2631,7 @@ reviews. Googlers can read more about this at go/gwsq-gerrit.
 </histogram>
 
 <histogram name="Android.WebView.NonEmbeddedMetrics.NumHistograms"
-    units="histograms" expires_after="2021-01-20">
+    units="histograms" expires_after="2021-07-20">
   <owner>ntfschr@chromium.org</owner>
   <owner>hazems@chromium.org</owner>
   <owner>src/android_webview/OWNERS</owner>
@@ -2644,7 +2644,7 @@ reviews. Googlers can read more about this at go/gwsq-gerrit.
 
 <histogram name="Android.WebView.NonEmbeddedMetrics.ParsingLogResult"
     enum="AndroidWebViewNonEmbeddedMetricsParsingLogResult"
-    expires_after="2021-01-20">
+    expires_after="2021-07-20">
   <owner>hazems@chromium.org</owner>
   <owner>ntfschr@chromium.org</owner>
   <owner>src/android_webview/OWNERS</owner>
@@ -2658,7 +2658,7 @@ reviews. Googlers can read more about this at go/gwsq-gerrit.
 
 <histogram name="Android.WebView.NonEmbeddedMetrics.RetrieveMetricsTaskStatus"
     enum="AndroidWebViewNonEmbeddedMetricsRetrieveMetricsTaskStatus"
-    expires_after="2021-01-20">
+    expires_after="2021-07-20">
   <owner>hazems@chromium.org</owner>
   <owner>ntfschr@chromium.org</owner>
   <owner>src/android_webview/OWNERS</owner>
@@ -2670,7 +2670,7 @@ reviews. Googlers can read more about this at go/gwsq-gerrit.
 </histogram>
 
 <histogram name="Android.WebView.NonEmbeddedMetrics.TransmissionResult"
-    enum="AndroidWebViewDevUiMetricsTransmission" expires_after="2021-01-20">
+    enum="AndroidWebViewDevUiMetricsTransmission" expires_after="2021-07-20">
   <owner>ntfschr@chromium.org</owner>
   <owner>hazems@chromium.org</owner>
   <owner>src/android_webview/OWNERS</owner>