Invoke GetInlineCost for legality check before inline functions in SampleProfileLoader.

Summary: SampleProfileLoader inlines hot functions if it is inlined in the profiled binary. However, the inline needs to be guarded by legality check, otherwise it could lead to correctness issues.

Reviewers: eraman, davidxl

Reviewed By: eraman

Subscribers: vitalybuka, sanjoy, llvm-commits

Differential Revision: https://reviews.llvm.org/D37779

llvm-svn: 313277