Avoid heap allocation for binary search work stack.
Avoid heap allocation for binary search work stack.

During switch lowering a binary search tree is created. The height of this
tree is usually small so no need for heap allocation.

BUG=
R=jvoung@chromium.org, jvoung, stichnot

Review URL: https://codereview.chromium.org/1240323005.

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