Revert of [serializer] add test case for unknown external references.

src/snapshot/serializer-common.cc

Index: src/snapshot/serializer-common.cc
diff --git a/src/snapshot/serializer-common.cc b/src/snapshot/serializer-common.cc
index 6c400cd25ea2c9dfe1cd08a0c6bdf486e2bc8666..baab8f3d6b26aca39cd98688b0d83def58ba0c0f 100644
--- a/src/snapshot/serializer-common.cc
+++ b/src/snapshot/serializer-common.cc
@@ -7,10 +7,6 @@
 #include "src/external-reference-table.h"
 #include "src/ic/stub-cache.h"
 #include "src/list-inl.h"
-
-#if defined(DEBUG) && defined(V8_OS_LINUX)
-#include <execinfo.h>
-#endif  // DEBUG && V8_OS_LINUX
 
 namespace v8 {
 namespace internal {
@@ -37,14 +33,7 @@
   DCHECK_NOT_NULL(address);
   base::HashMap::Entry* entry =
       const_cast<base::HashMap*>(map_)->Lookup(address, Hash(address));
-  if (entry == nullptr) {
-    void* function_addr = address;
-    v8::base::OS::PrintError("Unknown external reference %p.\n", function_addr);
-#if defined(DEBUG) && defined(V8_OS_LINUX)
-    v8::base::OS::PrintError("%s\n", backtrace_symbols(&function_addr, 1)[0]);
-#endif  // DEBUG && V8_OS_LINUX
-    v8::base::OS::Abort();
-  }
+  DCHECK_NOT_NULL(entry);
   return static_cast<uint32_t>(reinterpret_cast<intptr_t>(entry->value));
 }