Fix TryCatch.ReThrow() to not clobber Message.

Fix TryCatch.ReThrow() to not clobber Message.

TryCatch.ReThrow() sets a flag which, in the TryCatch destructor,
throws the caught exception using the public v8::ThrowException().
When the TryCatch catches the exception, the pending Message
object is saved internally, but the MessageLocation information is
not.  When the TryCatch is destructed, the Message object is not
re-set in the engine, so the Isolate::DoThrow() that the ReThrow()
triggers winds up creating a new Message object.  This alters the
reported location of the re-thrown exception to be the location of
the TryCatch.

This patch modifies the TryCatch to store the MessageLocation data
as well as the Message object and adds a new Isolate::RestoreMessage()
call which the destructor uses to re-set the Message object and
MessageLocation data within the Isolate TLS prior to calling the
public v8::ThrowException().  Since Isolate::RestoreMessage() is
always followed by a Isolate::DoThrow(), a restore_message_ flag is
set and Isolate::DoThrow() does not re-create the Message if set.

TEST=cctest/test-api/TryCatchNestedSyntax

[apaprocki, 2013-06-01 22:09:38]

This change removes the need for this hack in Node:

https://github.com/joyent/node/blob/master/src/node_script.cc#L414

As a result of this, a few Node bugs in the vm module should be fixed:

https://github.com/joyent/node/issues/1310
https://github.com/joyent/node/issues/3452

https://github.com/joyent/node/pull/3570 (would be closed)

I tried to do this without needing the restoring_message_ flag, but simply
checking if pending_message_obj_->IsTheHole() breaks throws in finally clauses
since those *do* want to overwrite the current exception.

Added a test, verified it fixes it, and also verified it fixes the Node issues.

[Yang, 2013-06-25 15:51:19]

On 2013/06/03 12:09:08, apaprocki wrote:

LGTM, but I wanted to change somethings, so I created a new CL based on this
one: https://codereview.chromium.org/17694002/

Please take a look there before I land it. Thanks!