[esan|cfrag] Minor cfrag report adjustment

Summary:
Reports the struct field access info only if it has been used at least
once.

Adds type printing size limit.

Formats the cache_frag.cpp with clang-format.

Reviewers: bruening

Subscribers: llvm-commits, eugenis, kcc, zhaoqin, vitalybuka, aizatsky, kubabrecka

Differential Revision: http://reviews.llvm.org/D21351

llvm-svn: 272810