clang/win: Fix build after https://codereview.chromium.org/1456663003

Fixes:
..\..\sandbox\win\src\sandbox_policy_base.cc(165,5) : error: delete called on
        'sandbox::PolicyBase' that has virtual functions but non-virtual
        destructor [-Werror,-Wdelete-non-virtual-dtor]
    delete this;
    ^
BUG=82385
R=rickyz@chromium.org
TBR=wfh

Review URL: https://codereview.chromium.org/1521703003 .

Cr-Commit-Position: refs/heads/master@{#364933}
1 file changed