Shift+F10 should open Context Menu regardless the state of NumLock/CapsLock

Before CL Shift+F10 won't open Context Menu when NumLock or CapsLock is
on, which is confusing and does not match ContextMenu key nor other browsers.

e.g.
1. On Chrome NumLock+ContextMenu opens CM
2. On Firefox NumLock+Shift+F10 opens CM
But on Chrome NumLock+Shift+F10 won't open CM.

After CL Chrome will match Firefox, Windows Notepad, IE, plus ContextMenu key's
behavior.

BUG=6941

Review-Url: https://codereview.chromium.org/2122053003
Cr-Commit-Position: refs/heads/master@{#404194}
4 files changed