MacViews: Views accelerators table should match the Cocoa one.

Updated views/accelerator_table.cc to match accelerators_cocoa.mm. Added
eligible shortcuts from global_keyboard_shortcuts_mac.mm as well.

Also handle the case when the user configured cmd-left to mean "previous tab",
as it should take precedence over the built-in binding: we're consulting the
[NSApp mainMenu] using CommandForKeyEvent().

Lastly, the Cmd+{/} shortcuts are special as they would be impossible to
perform on German and French keyboard layouts if we would simply check for
keycodes as we do in accelerator_table.cc (crbug.com/25946).

In order to tackle last two problems I've added PreHandleKeyboardEvent and
HandleKeyboardEvent to the NativeBrowserFrame interface.

BUG=620315

Review-Url: https://codereview.chromium.org/2074643003
Cr-Commit-Position: refs/heads/master@{#433574}
21 files changed