Removed StartProvisionalNavigationExitedWithEmptyNavigationManager metric.

ios/web/web_state/ui/crw_web_controller.mm

Index: ios/web/web_state/ui/crw_web_controller.mm
diff --git a/ios/web/web_state/ui/crw_web_controller.mm b/ios/web/web_state/ui/crw_web_controller.mm
index 45a5e8b1532b33c6905f7aac8b831d5925d9bfbf..faac543773be34e1fa12ee45d23f6ef9d884f5f6 100644
--- a/ios/web/web_state/ui/crw_web_controller.mm
+++ b/ios/web/web_state/ui/crw_web_controller.mm
@@ -4599,18 +4599,6 @@ const NSTimeInterval kSnapshotOverlayTransition = 0.5;
     }
   }
 
-  if (![self currentSessionEntry]) {
-    // In this state CRWWebController will crash in |didCommitNavigation:|
-    // (crbug.com/676458). It's unclear if web controller could get into this
-    // state but it's one of the guesses for crbug.com/676458 root cause. Report
-    // UMA historgam if that happens.
-    // TODO(crbug.com/677552): Remove this historgam.
-    UMA_HISTOGRAM_BOOLEAN(
-        "WebController."
-        "StartProvisionalNavigationExitedWithEmptyNavigationManager",
-        true);
-  }
-
   // Ensure the URL is registered and loadPhase is as expected.
   DCHECK(_lastRegisteredRequestURL == webViewURL);
   DCHECK(self.loadPhase == web::LOAD_REQUESTED);