ios: Remove application.backgroundTimeRemaining.

Remove this for a milestone to see if hangs go down.

Bug: 1150659
Change-Id: Ief95b225bceaeb9a565149f7a9ac4260e6b3cd99
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2547328Reviewed-by: Rohit Rao <rohitrao@chromium.org>
Reviewed-by: Eugene But <eugenebut@chromium.org>
Commit-Queue: Justin Cohen <justincohen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#829024}

base/ios/scoped_critical_action.mm

@@ -46,12 +46,6 @@ void ScopedCriticalAction::Core::StartBackgroundTask(scoped_refptr<Core> core,
     return;
   }
 
-  NSTimeInterval time = application.backgroundTimeRemaining;
-  if (time != DBL_MAX && time > 0) {
-    UMA_HISTOGRAM_MEDIUM_TIMES("IOS.CriticalActionBackgroundTimeRemaining",
-                               base::TimeDelta::FromSeconds(time));
-  }
-
   AutoLock lock_scope(core->background_task_id_lock_);
   NSString* task_string =
       !task_name.empty() ? base::SysUTF8ToNSString(task_name) : nil;