Debugger: require debugger to be active when dealing with breaks.

Debugger: require debugger to be active when dealing with breaks.

This invariant will save us some head ache.
The changes to test-debug/DebugStub is due to the fact that it abuses
the ability to set break points in code that has no debug break slots.
This is now no longer possible.

R=ulan@chromium.org
BUG=v8:4132
LOG=N

Committed: https://crrev.com/75350f1ef0ebf189ef3583183eae694a25597fc0
Cr-Commit-Position: refs/heads/master@{#29038}

[ulan, 2015-06-15 10:41:35]

lgtm

[Yang, 2015-06-15 12:00:26]

The CQ bit was checked by yangguo@chromium.org

[commit-bot: I haz the power, 2015-06-15 12:00:34]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1181013007/1

[commit-bot: I haz the power, 2015-06-15 12:23:59]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2015-06-15 12:24:00]

Try jobs failed on following builders:
  v8_linux_nodcheck_rel on tryserver.v8 (JOB_FAILED,
http://build.chromium.org/p/tryserver.v8/builders/v8_linux_nodcheck_rel/build...)

[Yang, 2015-06-16 06:36:52]

The CQ bit was checked by yangguo@chromium.org

[Yang, 2015-06-16 06:36:53]

The patchset sent to the CQ was uploaded after l-g-t-m from ulan@chromium.org
Link to the patchset: https://codereview.chromium.org/1181013007/#ps20001
(title: "fix yet another test")

[commit-bot: I haz the power, 2015-06-16 06:37:01]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1181013007/20001

[commit-bot: I haz the power, 2015-06-16 07:11:17]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-06-16 07:11:33]

Patchset 2 (id:??) landed as
https://crrev.com/75350f1ef0ebf189ef3583183eae694a25597fc0
Cr-Commit-Position: refs/heads/master@{#29038}