Don't allow deferred frames to create new windows.

third_party/WebKit/Source/web/ChromeClientImpl.cpp

Index: third_party/WebKit/Source/web/ChromeClientImpl.cpp
diff --git a/third_party/WebKit/Source/web/ChromeClientImpl.cpp b/third_party/WebKit/Source/web/ChromeClientImpl.cpp
index ab5b0e7b38da10ede99bb915ea7f6405b1e21267..3d0bf95dd324a920a57a37ca0f3cd260e3805720 100644
--- a/third_party/WebKit/Source/web/ChromeClientImpl.cpp
+++ b/third_party/WebKit/Source/web/ChromeClientImpl.cpp
@@ -355,6 +355,9 @@ Page* ChromeClientImpl::createWindow(LocalFrame* frame, const FrameLoadRequest&
     if (!m_webView->client())
         return nullptr;
 
+    if (!frame->page() || frame->page()->defersLoading())
+        return nullptr;
+
     WebNavigationPolicy policy = effectiveNavigationPolicy(navigationPolicy, features);
     DCHECK(frame->document());
     Fullscreen::fullyExitFullscreen(*frame->document());