Merged r16039, r16067 into trunk branch.

Add start and end profiling time to v8::CpuProfile

Return start/end profiling time in microseconds instead of milliseconds

BUG=267595,v8:2824
R=dslomov@chromium.org

Review URL: https://codereview.chromium.org/22634010

git-svn-id: https://v8.googlecode.com/svn/trunk@16142 ce2b1a6d-e550-0410-aec6-3dcde31c8c00