Stop injection when injections are invalidated

extensions/renderer/script_injection.h

Index: extensions/renderer/script_injection.h
diff --git a/extensions/renderer/script_injection.h b/extensions/renderer/script_injection.h
index 7b501f40e1da0bd0240760647cfd708a6616071c..af71f7a87f07ece84a2db7255fc0c2fa869c895a 100644
--- a/extensions/renderer/script_injection.h
+++ b/extensions/renderer/script_injection.h
@@ -41,6 +41,7 @@ class ScriptInjection {
   enum InjectionResult {
     INJECTION_FINISHED,
     INJECTION_BLOCKED,
+    INJECTION_CANCELED,
     INJECTION_WAITING
   };
 
@@ -95,6 +96,8 @@ class ScriptInjection {
 
   // Injects the script. Returns INJECTION_FINISHED if injection has finished,
   // otherwise INJECTION_BLOCKED.
+  // The caller must not destruct this ScriptInjection instance during the call.
+  // Similarly, this instance must not delete itself during the call.
   InjectionResult Inject(ScriptsRunInfo* scripts_run_info);
 
   // Inject any JS scripts into the frame for the injection.