Preserve message when rethrowing exception

A new message was always generated if there is a the top-most verbose
TryCatch, even when rethrowing an exception from a TryCatch that is going
out of scope, and we already have a message.

BUG=v8:3583
LOG=Y
R=yangguo@chromium.org

Review URL: https://codereview.chromium.org/587703002

Patch from Jens Widell <jl@opera.com>.

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@24152 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/isolate.cc

@@ -1019,9 +1019,9 @@ void Isolate::DoThrow(Object* exception, MessageLocation* location) {
       ShouldReportException(&can_be_caught_externally, catchable_by_javascript);
   bool report_exception = catchable_by_javascript && should_report_exception;
   bool try_catch_needs_message =
-      can_be_caught_externally && try_catch_handler()->capture_message_ &&
-      !thread_local_top()->rethrowing_message_;
+      can_be_caught_externally && try_catch_handler()->capture_message_;
   bool bootstrapping = bootstrapper()->IsActive();
+  bool rethrowing_message = thread_local_top()->rethrowing_message_;
 
   thread_local_top()->rethrowing_message_ = false;
 
@@ -1031,7 +1031,7 @@ void Isolate::DoThrow(Object* exception, MessageLocation* location) {
   }
 
   // Generate the message if required.
-  if (report_exception || try_catch_needs_message) {
+  if (!rethrowing_message && (report_exception || try_catch_needs_message)) {
     MessageLocation potential_computed_location;
     if (location == NULL) {
       // If no location was specified we use a computed one instead.