Add |RTCUIApplicationStatusObserver sharedInstance| call in ios test AppDelegate.

webrtc/test/ios/test_support.mm

Index: webrtc/test/ios/test_support.mm
diff --git a/webrtc/test/ios/test_support.mm b/webrtc/test/ios/test_support.mm
index 9a9035612a08dd931f979357462fb4de12eec436..a01b03c9f0114ae28249ba3ee913b34acaea9716 100644
--- a/webrtc/test/ios/test_support.mm
+++ b/webrtc/test/ios/test_support.mm
@@ -12,6 +12,8 @@
 
 #include "webrtc/test/ios/test_support.h"
 
+#import "webrtc/sdk/objc/Framework/Classes/Common/RTCUIApplicationStatusObserver.h"
+
 // Springboard will kill any iOS app that fails to check in after launch within
 // a given time. Starting a UIApplication before invoking TestSuite::Run
 // prevents this from happening.
@@ -60,6 +62,11 @@ static char **g_argv;
   // root view controller. Set an empty one here.
   [_window setRootViewController:[[UIViewController alloc] init]];
 
+  // We want to call `RTCUIApplicationStatusObserver sharedInstance` as early as
+  // possible in the application lifecycle to set observation properly.
+  __unused RTCUIApplicationStatusObserver *observer =
+      [RTCUIApplicationStatusObserver sharedInstance];
+
   // Queue up the test run.
   [self performSelector:@selector(runTests) withObject:nil afterDelay:0.1];
   return YES;