- (y << L + x) & (-1 << L) => (x & (-1 << L)) + y << L
- (x + y << L) & (-1 << L) => (x & (-1 << L)) + y << L

TEST=unittests
R=jarin@chromium.org

Review URL: https://codereview.chromium.org/758603003

Cr-Commit-Position: refs/heads/master@{#25627}