Check that constant is an integer before getting its value in HGraphBuilder::MatchRotateRight.

BUG=351263
LOG=N
TEST=mjsunit/regress/regress-351263
R=svenpanne@chromium.org

Review URL: https://codereview.chromium.org/197803005

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@19890 ce2b1a6d-e550-0410-aec6-3dcde31c8c00