Add instcombine pass if sampleprofile pass is enabled.

Summary: Sample profile pass need to have instcombine pass. A related change is http://reviews.llvm.org/D17742. But we should not explicitly add dependency between to non-analysis passes. So we add the dependency here.

Reviewers: davidxl, dnovillo

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D20502

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@271010 91177308-0d34-0410-b5e6-96231b3b80d8