Verify that an event queue is present before firing an event.

third_party/WebKit/Source/core/frame/csp/ContentSecurityPolicy.cpp

Index: third_party/WebKit/Source/core/frame/csp/ContentSecurityPolicy.cpp
diff --git a/third_party/WebKit/Source/core/frame/csp/ContentSecurityPolicy.cpp b/third_party/WebKit/Source/core/frame/csp/ContentSecurityPolicy.cpp
index 10c3665d7f81fa19c4a74df0672861de564d469d..4bf8c546801c00d1199a650c011a9898902ec592 100644
--- a/third_party/WebKit/Source/core/frame/csp/ContentSecurityPolicy.cpp
+++ b/third_party/WebKit/Source/core/frame/csp/ContentSecurityPolicy.cpp
@@ -1252,7 +1252,9 @@ void ContentSecurityPolicy::dispatchViolationEvents(
     const SecurityPolicyViolationEventInit& violationData,
     Element* element,
     Document* document) {
-  if (!document->domWindow())
+  // If the document is detached or closed (thus clearing its event queue)
+  // between the violation occuring and this event dispatch, exit early.
+  if (!document->domWindow() || !document->domWindow()->getEventQueue())
     return;
 
   SecurityPolicyViolationEvent* event = SecurityPolicyViolationEvent::create(