Interpret UIApplicationState correctly for TabUsageRecorder

UIApplicationState was incorrectly casted into a bool making
UIApplicationStateActive (which has a numerical value of 0) to be
incorrectly interpreted as "not active".

Fixing bug w/o unit test for now. Test will be updated in a
follow up CL.

Bug: 781361
Cq-Include-Trybots: master.tryserver.chromium.mac:ios-simulator-cronet;master.tryserver.chromium.mac:ios-simulator-full-configs
Change-Id: Ia7fd52a5809873777c01981079cde9c3fe5e8008
Reviewed-on: https://chromium-review.googlesource.com/802464Reviewed-by: Gregory Chatzinoff <gchatz@chromium.org>
Commit-Queue: Peter Lee <pkl@chromium.org>
Cr-Commit-Position: refs/heads/master@{#520797}

ios/chrome/browser/metrics/tab_usage_recorder.mm

@@ -451,8 +451,17 @@ void TabUsageRecorder::PageLoaded(
 }
 
 void TabUsageRecorder::RenderProcessGone(web::WebState* web_state) {
-  RendererTerminated(web_state, web_state->IsVisible(),
-                     [UIApplication sharedApplication].applicationState);
+  bool is_active;
+  switch ([UIApplication sharedApplication].applicationState) {
+    case UIApplicationStateActive:
+      is_active = true;
+      break;
+    case UIApplicationStateInactive:
+    case UIApplicationStateBackground:
+      is_active = false;
+      break;
+  }
+  RendererTerminated(web_state, web_state->IsVisible(), is_active);
 }
 
 void TabUsageRecorder::WebStateDestroyed(web::WebState* web_state) {