[iOS] Add a HasActiveStateManager method to BrowserState.

ios/web/browser_state.mm

Index: ios/web/browser_state.mm
diff --git a/ios/web/browser_state.mm b/ios/web/browser_state.mm
index 510140d2f898b86b8be01ab9ef38d4d572da88d1..6d1eeeb734738bba0fa3fc3c42c89b9b18550325 100644
--- a/ios/web/browser_state.mm
+++ b/ios/web/browser_state.mm
@@ -52,6 +52,12 @@ scoped_refptr<CertificatePolicyCache> BrowserState::GetCertificatePolicyCache(
 }
 
 // static
+bool BrowserState::HasActiveStateManager(BrowserState* browser_state) {
+  DCHECK_CURRENTLY_ON_WEB_THREAD(WebThread::UI);
+  return browser_state->GetUserData(kActiveStateManagerKeyName) != nullptr;
+}
+
+// static
 ActiveStateManager* BrowserState::GetActiveStateManager(
     BrowserState* browser_state) {
   DCHECK_CURRENTLY_ON_WEB_THREAD(WebThread::UI);