Introduce --zap-cpp-pointers (off by default)

src/isolate.h

 // Copyright 2012 the V8 project 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 V8_ISOLATE_H_
 #define V8_ISOLATE_H_
 
 #include <memory>
 #include <queue>
 
@@ skipping 596 matching lines @@
   THREAD_LOCAL_TOP_ADDRESS(Code*, pending_handler_code)
   THREAD_LOCAL_TOP_ADDRESS(intptr_t, pending_handler_offset)
   THREAD_LOCAL_TOP_ADDRESS(Address, pending_handler_fp)
   THREAD_LOCAL_TOP_ADDRESS(Address, pending_handler_sp)
 
   THREAD_LOCAL_TOP_ACCESSOR(bool, external_caught_exception)
 
   v8::TryCatch* try_catch_handler() {
     return thread_local_top_.try_catch_handler();
   }
+#if DEBUG
+  static v8::TryCatch* next_try_catch(v8::TryCatch* try_catch) {
+    return try_catch->next_;
+  }
+#endif
   bool* external_caught_exception_address() {
     return &thread_local_top_.external_caught_exception_;
   }
 
   THREAD_LOCAL_TOP_ADDRESS(Object*, scheduled_exception)
 
   inline void clear_pending_message();
   Address pending_message_obj_address() {
     return reinterpret_cast<Address>(&thread_local_top_.pending_message_obj_);
   }
@@ skipping 1187 matching lines @@
 
   EmbeddedVector<char, 128> filename_;
   FILE* file_;
   int scope_depth_;
 };
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_ISOLATE_H_