Classes: Add support for stepping through default constructors

If a class extends another class and it doesn't provide a constructor,
one is created for them. We therefore need to ensure that stepping into
the constructor steps into the super class constructor.

BUG=v8:3674
LOG=Y
R=dslomov@chromium.org, aandrey , yurys

Review URL: https://codereview.chromium.org/725983002

Cr-Commit-Position: refs/heads/master@{#25366}