Format notification trigger timestamp in devtools.

Instead of showing the raw timestamp as a number, format it according to
ISO8601. Example output: Show Trigger Timestamp: 2019-10-11T14:56:38.351Z
This will always use UTC as timezone.

Bug: 1004118
Change-Id: I1f6b3980915cf24dea2bc896400587aa4b55dccd
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1855969Reviewed-by: Rayan Kanso <rayankans@chromium.org>
Commit-Queue: Richard Knoll <knollr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#705139}

content/browser/notifications/devtools_event_logging.cc

@@ -7,6 +7,7 @@
 #include "base/callback.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/utf_string_conversions.h"
+#include "base/time/time_to_iso8601.h"
 #include "content/public/browser/browser_context.h"
 #include "content/public/browser/devtools_background_services_context.h"
 #include "content/public/browser/notification_database_data.h"
@@ -115,8 +116,7 @@ void LogNotificationScheduledEventToDevTools(
 
   std::move(callback).Run(
       /* event_name= */ "Notification scheduled",
-      {{"Show Trigger Timestamp",
-        base::NumberToString(show_trigger_timestamp.ToJsTime())},
+      {{"Show Trigger Timestamp", base::TimeToISO8601(show_trigger_timestamp)},
        {"Title", base::UTF16ToUTF8(data.notification_data.title)},
        {"Body", base::UTF16ToUTF8(data.notification_data.body)}});
 }