[Mac] Fix the build

Mac build is failing due to Clang being picky about:

[chromium-style] virtual methods with non-empty bodies shouldn't be declared inline.
[chromium-style] Complex constructor has an inlined body.
[chromium-style] Complex class/struct needs an explicit out-of-line destructor.
[chromium-style] virtual methods with non-empty bodies shouldn't be declared inline.

http://www.chromium.org/developers/coding-style/chromium-style-checker-errors