Add crash keys to LocalDOMWindow to help diagnose bug 621730.

third_party/WebKit/Source/wtf/debug/CrashLogging.h

Index: third_party/WebKit/Source/wtf/debug/CrashLogging.h
diff --git a/third_party/WebKit/Source/wtf/debug/CrashLogging.h b/third_party/WebKit/Source/wtf/debug/CrashLogging.h
new file mode 100644
index 0000000000000000000000000000000000000000..a4fd960edc939baf914b07eb7d9cd57e2ee2eab4
--- /dev/null
+++ b/third_party/WebKit/Source/wtf/debug/CrashLogging.h
@@ -0,0 +1,19 @@
+// Copyright 2016 The Chromium Authors. All rights reserved.

[Robert Sesek, 2016/06/28 14:25:56]

Can this be split out into a separate CL? Since the crash keys are temporary,
that would make it easier to revert later.

[Yuki, 2016/06/28 23:09:53]

Already done at https://codereview.chromium.org/2105763002/

+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef WTF_CrashLogging_h
+#define WTF_CrashLogging_h
+
+#include "base/debug/crash_logging.h"
+#include "wtf/WTFExport.h"
+
+namespace WTF {
+namespace debug {
+
+using ScopedCrashKey = base::debug::ScopedCrashKey;
+
+} // namespace debug
+} // namespace WTF
+
+#endif // WTF_CrashLogging_h