Revert of Add explicit destructors to DOM classes containing smart pointers to incomplete types

Revert of Add explicit destructors to DOM classes containing smart pointers to incomplete types (patchset #2 id:20001 of https://codereview.chromium.org/412483007/)

Reason for revert:
This should no longer be necessary; clang should be able to handle this now. Reverting this to test that theory.

Original issue's description:
> Add explicit destructors to DOM classes containing smart pointers to incomplete types
> 
> Clang on Windows tries to declare the implicit virtual destructor of
> these classes so that it can diagnose mismatched exceptions
> specifications. This ends up requiring that the type of the smart
> pointer be complete, which it is not. This codepath does not fire on
> non-Windows platforms due to the Itanium C++ ABI key function
> optimization.
> 
> It is possible to fix Clang to avoid performing semantic analysis of the
> destructor when it only needs to compute the exception specification,
> but it is prohibitively difficult.  http://llvm.org/PR20337
> 
> Another possible fix on the Blink side would be to make the smart
> pointer type complete by including the relevant header, which has the
> cost of increasing transitive header bloat. Instead, simply define the
> destructor out of line. This is also a minor object file size
> optimization, as now the destructor is only emitted once.
> 
> R=thakis@chromium.org
> BUG=82385
> 
> Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=178838

TBR=rnk@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=82385
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=189052

[Nico, 2015-01-27 19:42:49]

Created Revert of Add explicit destructors to DOM classes containing smart
pointers to incomplete types

[commit-bot: I haz the power, 2015-01-27 19:43:30]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/878273002/1

[commit-bot: I haz the power, 2015-01-27 19:44:28]

Committed patchset #1 (id:1) as
https://src.chromium.org/viewvc/blink?view=rev&revision=189052

[Reid Kleckner, 2015-01-27 21:19:09]

lgtm