[Mac] Redo NSException handling, and generate better stacks for C++ exceptions.

base/mac/call_with_eh_frame.h

Index: base/mac/call_with_eh_frame.h
diff --git a/base/mac/call_with_eh_frame.h b/base/mac/call_with_eh_frame.h
new file mode 100644
index 0000000000000000000000000000000000000000..1f7d5e0dec80c291efff67930a70c552e8f678d1
--- /dev/null
+++ b/base/mac/call_with_eh_frame.h
@@ -0,0 +1,26 @@
+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef BASE_MAC_CALL_WITH_EH_FRAME_H_
+#define BASE_MAC_CALL_WITH_EH_FRAME_H_
+
+#include "base/base_export.h"
+
+namespace base {
+namespace mac {
+
+// Invokes the specified block in a stack frame with a special exception
+// handler. This function creates an exception handling stack frame that
+// specifies a custom C++ exception personality routine, which terminates the
+// search for an exception handler at this frame.
+//
+// The purpose of this function is to prevent a try/catch statement in system
+// libraries, acting as a global exception handler, from handling exceptions
+// in such a way that disrupts the generation of useful stack traces.
+void BASE_EXPORT CallWithEHFrame(void (^block)(void));
+
+}  // namespace mac
+}  // namespace base
+
+#endif  // BASE_MAC_CALL_WITH_EH_FRAME_H_