Subzero: Use SmallVector<> instead of vector<> in a couple places.
Subzero: Use SmallVector<> instead of vector<> in a couple places.

BUG= none
R=jvoung@chromium.org

Review URL: https://codereview.chromium.org/848603002

bkaradzic/SwiftShader,google/swiftshader,google/swiftshader,google/swiftshader,bkaradzic/SwiftShader,bkaradzic/SwiftShader,bkaradzic/SwiftShader,bkaradzic/SwiftShader