Review URL: https://codereview.chromium.org/1130133003

Cr-Commit-Position: refs/heads/master@{#28439}

Gather references to unbound variables where the reference (VariableProxy) is
inside strong mode. Check them against the global object when a script is bound
to a context (during compilation).

This CL only checks unbound variables which are not inside lazy functions - TBD
how do we solve that; alternatives: add developer mode which disables laziness /
do the check whenever lazy functions are really compiled.

BUG=v8:3956
LOG=N

Review URL: https://codereview.chromium.org/1005063002

Cr-Commit-Position: refs/heads/master@{#27422}

In addition to Parser, other phases (such as scope analysis) need to handle
compilation errors in the future. PendingCompilationErrorHandled takes care of
error handling in a unified way.

Split from https://codereview.chromium.org/943543002/ .

R=rossberg@chromium.org
BUG=

Review URL: https://codereview.chromium.org/960543002

Cr-Commit-Position: refs/heads/master@{#26853}