Add crash keys to LocalDOMWindow to help diagnose bug 621730.

third_party/WebKit/Source/core/frame/LocalDOMWindow.cpp

Index: third_party/WebKit/Source/core/frame/LocalDOMWindow.cpp
diff --git a/third_party/WebKit/Source/core/frame/LocalDOMWindow.cpp b/third_party/WebKit/Source/core/frame/LocalDOMWindow.cpp
index f6573e38431fe5c1f24825e2a4c473edb2563d4e..e9375a1c6b5eb725027b5fb3c177a258dc80d168 100644
--- a/third_party/WebKit/Source/core/frame/LocalDOMWindow.cpp
+++ b/third_party/WebKit/Source/core/frame/LocalDOMWindow.cpp
@@ -79,6 +79,7 @@
 #include "public/platform/Platform.h"
 #include "public/platform/WebFrameScheduler.h"
 #include "public/platform/WebScreenInfo.h"
+#include "wtf/debug/CrashLogging.h"
 #include <memory>
 
 namespace blink {
@@ -687,6 +688,12 @@ void LocalDOMWindow::postMessageTimerFired(PostMessageTimer* timer)
     UserGestureIndicator gestureIndicator(timer->userGestureToken());
 
     event->entangleMessagePorts(document());
+
+    // Temporary instrumentation for http://crbug.com/621730.
+    WTF::debug::ScopedCrashKey("postmessage_src_origin", event->origin().utf8().data());
+    WTF::debug::ScopedCrashKey("postmessage_dst_origin", document()->getSecurityOrigin()->toRawString().utf8().data());
+    WTF::debug::ScopedCrashKey("postmessage_dst_url", document()->url().getString().utf8().data());
+
     dispatchMessageEventWithOriginCheck(timer->targetOrigin(), event, timer->takeLocation());
 }