Reverted r576 as it caused a regression.

src/execution.cc

 // Copyright 2006-2008 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 73 matching lines @@
 
     // Call the function through the right JS entry stub.
     value = CALL_GENERATED_CODE(entry, func->code()->entry(), *func,
                                 *receiver, argc, args);
   }
 
 #ifdef DEBUG
   value->Verify();
 #endif
 
-  // Update the pending exception and external caught flag and return the value.
+  // Update the pending exception flag and return the value.
   *has_pending_exception = value->IsException();
   ASSERT(*has_pending_exception == Top::has_pending_exception());
-  Top::propagate_external_caught();
+  if (*has_pending_exception) {
+    Top::setup_external_caught();
+  }
 
   // If the pending exception is OutOfMemoryException set out_of_memory in
   // the global context.  Note: We have to mark the global context here
   // since the GenerateThrowOutOfMemory stub cannot make a RuntimeCall to
   // set it.
   if (*has_pending_exception) {
     if (Top::pending_exception() == Failure::OutOfMemoryException()) {
       Top::context()->mark_out_of_memory();
     }
   }
@@ skipping 412 matching lines @@
   // All allocation spaces other than NEW_SPACE have the same effect.
   Heap::CollectGarbage(0, OLD_DATA_SPACE);
   return v8::Undefined();
 }
 
 
 static GCExtension kGCExtension;
 v8::DeclareExtension kGCExtensionDeclaration(&kGCExtension);
 
 } }  // namespace v8::internal