Get rid of duplicated CPU::DebugBreak() method.

We already have OS::DebugBreak(), which does the right thing.

R=jkummerow@chromium.org

Review URL: https://codereview.chromium.org/22893050

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@16293 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Add comment about avoiding VS runtime support to OS::DebugBreak.

R=mstarzinger@chromium.org

Review URL: https://codereview.chromium.org/23090004

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@16294 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Get rid of ConvertFieldToDescriptor and simplify related code.

R=rossberg@chromium.org

Review URL: https://chromiumcodereview.appspot.com/22861025

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@16295 ce2b1a6d-e550-0410-aec6-3dcde31c8c00