AllocateAlignedMemory calls ReserveAlignedMemory which increments size_
value. In some cases AllocateAlignedMemory can return NULL value. Before
returning NULL, AllocateAlignedMemory should decrease size_ value.

TEST=cctest/test-spaces/LargeObjectSpace
BUG=

Review-Url: https://codereview.chromium.org/2418733002
Cr-Commit-Position: refs/heads/master@{#40262}