Remove implementation of CpuProfileNode methods deprecated in v8 3.20

GetTotalTime, GetSelfTime and GetTotalSamplesCount were deprecated in 3.20 (https://code.google.com/p/v8/source/browse/branches/3.20/include/v8-profiler.h) and can be safely removed.

BUG=None
R=bmeurer@chromium.org, loislo@chromium.org

Review URL: https://codereview.chromium.org/23554002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@16367 ce2b1a6d-e550-0410-aec6-3dcde31c8c00