After parsing a function, if there's no masking declaration in the function scope, DeclareFunctionVar will also bind the function name to a variable. It will either bind it to the const/const-legacy function_ variable, or to a dynamic non-local if the function calls sloppy eval.

Even if the variable is masked or sloppy eval is called, we still declare the function-var. The client immediately sets up the variable by assigning the resulting function to it.

BUG=v8:5209

Review-Url: https://codereview.chromium.org/2274133002
Cr-Commit-Position: refs/heads/master@{#39581}