DFG compile time measurements should really report milliseconds

DFG compile time measurements should really report milliseconds
https://bugs.webkit.org/show_bug.cgi?id=142209

Reviewed by Benjamin Poulain.

Source/JavaScriptCore:

Fix this to record milliseconds instead of seconds.

* dfg/DFGPlan.cpp:
(JSC::DFG::Plan::compileInThread):
(JSC::DFG::Plan::compileInThreadImpl):

Source/WTF:

This bug was introduced because currentTimeMS() calls were converted to
monotonicallyIncreasingTime() calls. Perhaps this bug would be less likely if there was a
monotonicallyIncreasingTimeMS() function available, so this patch adds it.

* wtf/CurrentTime.h:
(WTF::monotonicallyIncreasingTimeMS):

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@180919 268f45cc-cd09-0410-ab3c-d52691b4dbfc