V8InspectorSession::schedulePauseOnNextStatement and V8InspectorSession::cancelPauseOnNextStatement are now exposed in inspector tests. These methods are required at least for better blackboxing tests.

BUG=v8:5842
R=dgozman@chromium.org

Review-Url: https://codereview.chromium.org/2636613002
Cr-Commit-Position: refs/heads/master@{#42469}