[ios] Automatically fail any WebTest whose render process crashes.

ios/web/public/web_state/global_web_state_observer.h

Index: ios/web/public/web_state/global_web_state_observer.h
diff --git a/ios/web/public/web_state/global_web_state_observer.h b/ios/web/public/web_state/global_web_state_observer.h
index 53c973a20c56dba6cd3742d78e27403f03391250..2df5b560730958dc796f511fe385ae90d9d89b1b 100644
--- a/ios/web/public/web_state/global_web_state_observer.h
+++ b/ios/web/public/web_state/global_web_state_observer.h
@@ -45,6 +45,10 @@ class GlobalWebStateObserver {
   virtual void PageLoaded(WebState* web_state,
                           PageLoadCompletionStatus load_completion_status) {}
 
+  // Called when the web process is terminated (usually by crashing, though
+  // possibly by other means).
+  virtual void RenderProcessGone(WebState* web_state) {}
+
   // Called when |web_state| is being destroyed.
   virtual void WebStateDestroyed(WebState* web_state) {}