DevTools: Fix how JavaScriptOutlineDialog works when the function name is too long.

R=pfeldman, lushnikov

Review URL: https://codereview.chromium.org/189913008

git-svn-id: svn://svn.chromium.org/blink/trunk@168917 bbb929c8-8fbe-4397-9dbb-9b2b20218538