This patch:
- Adds MOZ_MUST_USE to AllocPolicy::checkSimulatedOOM().
- Adds MOZ_MUST_USE to LZ4::decompress() (both variants) and fixes their
comments.
- Changes the return type of SplayTree::insert() from bool to void, because it
always returns true and its callers don't check the return value.
- Changes the return type of SplayTree::finishInsertion() from T* to void,
because it makes things clearer -- it was just returning the aNew argument.
- Adds MOZ_MUST_USE to a Vector::growTo() (both variants).
