ConstantPoolSizeAt() should return number of Instructions instead, otherwise, some of the code will be treated as constant pool when printing code in ARM disassembler.

BUG=none

TEST=none
R=bmeurer@chromium.org

Review URL: https://codereview.chromium.org/23654005

Patch from Bangfu Tao <bangfu.tao@samsung.com>.

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@16419 ce2b1a6d-e550-0410-aec6-3dcde31c8c00