Use a delegating constructor for CompilationInfo, reducing duplicated
code. Simplified handling of InlinedFunctionInfos on the way: When we
start compiling, we have bigger things to worry about than a default
vector.

Reduced the usage of a SharedFunctionInfo for compiling, this is a
slighty strange concept.

Review URL: https://codereview.chromium.org/1018853004

Cr-Commit-Position: refs/heads/master@{#27299}