This is a reland of 470a1001
Original change's description:
> Start migration of try/throw/catch to match proposal.
> 
> This CL does the first baby steps on moving the current (experimental)
> exception handling to match that of the WebAssembly proposal.
> 
> It does the following:
> 
> 1) Use exception tags instead of integers.
> 
> 2) Only handle empty exception signatures (i.e. no values associated
>    with the exception tag.
> 
> 3) Only handle one catch clause.
> 
> 4) Be sure to rethrow the exception if the exception tag does not match.
> 
> Note: There are many things that need to be fixed, and are too
> numerous to list here. However, the code should have TODO's on each
> missing parts of the implementation.
> 
> Also note that the code currently doesn't handle nested catch blocks,
> nor does it change the throw value being an integer. Rather, the
> integer value is still being thrown, and currently is the exception
> tag. Therefore, we don't build an exception object. This is the reason
> why this CL doesn't handle exceptions that pass values.
> 
> Also, the current implementation still can't handle multiple modules
> because tag resolution (between) modules has not be implemented yet.
> 
> Bug: v8:6577
> Change-Id: Id6d08b641b3c42d1eec7d4db582f2dab35406114
> Reviewed-on: https://chromium-review.googlesource.com/591910
> Reviewed-by: Brad Nelson <bradnelson@chromium.org>
> Commit-Queue: Karl Schimpf <kschimpf@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#47087}

Bug: v8:6577
Change-Id: I41c3309827c292cb787681a95aaef7cf9b931835
Reviewed-on: https://chromium-review.googlesource.com/598968Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Brad Nelson <bradnelson@chromium.org>
Commit-Queue: Brad Nelson <bradnelson@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47100}