Fix TryCatch.ReThrow() to not clobber Message.

src/api.cc

Index: src/api.cc
===================================================================
--- src/api.cc	(revision 14909)
+++ src/api.cc	(working copy)
@@ -2052,7 +2052,10 @@
     : isolate_(i::Isolate::Current()),
       next_(isolate_->try_catch_handler_address()),
       exception_(isolate_->heap()->the_hole_value()),
-      message_(i::Smi::FromInt(0)),
+      message_obj_(i::Smi::FromInt(0)),
+      message_script_(i::Smi::FromInt(0)),
+      message_start_pos_(0),
+      message_end_pos_(0),
       is_verbose_(false),
       can_continue_(true),
       capture_message_(true),
@@ -2068,6 +2071,17 @@
     v8::HandleScope scope(reinterpret_cast<Isolate*>(isolate_));
     v8::Local<v8::Value> exc = v8::Local<v8::Value>::New(Exception());
     isolate_->UnregisterTryCatchHandler(this);
+    if (HasCaught() && capture_message_) {
+      // If an exception was caught and rethrow_ is indicated, the saved
+      // message, script, and location need to be restored to Isolate TLS
+      // so that DoThrow() does not overwrite the values from the original
+      // exception with new ones computed at the current location.
+      i::Object* message = reinterpret_cast<i::Object*>(message_obj_);
+      i::Script* script = message_script_ ?
+        reinterpret_cast<i::Script*>(message_script_) : NULL;
+      isolate_->RestoreMessage(message, script,
+                               message_start_pos_, message_end_pos_);
+    }
     v8::ThrowException(exc);
   } else {
     isolate_->UnregisterTryCatchHandler(this);
@@ -2129,8 +2143,8 @@
 
 v8::Local<v8::Message> v8::TryCatch::Message() const {
   ASSERT(isolate_ == i::Isolate::Current());
-  if (HasCaught() && message_ != i::Smi::FromInt(0)) {
-    i::Object* message = reinterpret_cast<i::Object*>(message_);
+  if (HasCaught() && message_obj_ != i::Smi::FromInt(0)) {
+    i::Object* message = reinterpret_cast<i::Object*>(message_obj_);
     return v8::Utils::MessageToLocal(i::Handle<i::Object>(message, isolate_));
   } else {
     return v8::Local<v8::Message>();
@@ -2141,7 +2155,10 @@
 void v8::TryCatch::Reset() {
   ASSERT(isolate_ == i::Isolate::Current());
   exception_ = isolate_->heap()->the_hole_value();
-  message_ = i::Smi::FromInt(0);
+  message_obj_ = i::Smi::FromInt(0);
+  message_script_ = i::Smi::FromInt(0);
+  message_start_pos_ = 0;
+  message_end_pos_ = 0;
 }