DevTools: ignore WASD hotkeys in FlameChart if they come with ctrl/alt/meta

It's currently impossible to close devtools window with ^W due to the fact
that we ignore modifier keys when checking for the hotkey.

Review URL: https://codereview.chromium.org/511783002

git-svn-id: svn://svn.chromium.org/blink/trunk@180977 bbb929c8-8fbe-4397-9dbb-9b2b20218538