https://codereview.chromium.org/13925021/
If a non-POD class does not provide a default destructor, one is
provided by teh compiler. GCC will do so, but only at the point where the
vtable is output; since BlockRef has no implementation its destructor is
never output, so there is no complaint. VC++, however, provides the
destructor implementation as soon as it sees the type. If the destructor
of BlockRef is ever defined an error will be reported (since the
destructor of SkData is private).
Declaring (but does not defining) a destructor for BlockRef fixes two
issues. First, it prevents a default destructor from being provided,
removing the VC++ error. Second, BlockRef now blocks access to the
destructor through '->'.
git-svn-id: http://skia.googlecode.com/svn/trunk@8697 2bbb7eff-a529-9590-31e7-b0007b416f81
6f4cf2a195