RemoteMacViews: Break performKeyEquivalent and commandDispatch over mojo

This is another step towards supporting shortcut keys and menu interface
items in PWAs.

This breaks the following functions into a Cocoa component (for the
PWA process) and a Chrome component (for the browser process):
-[BrowserWindowCommandHandler commandDispatch]
-[BrowserWindowCommandHandler commandDispatchUsingKeyModifiers]
-[ChromeCommandDispatcherDelegate prePerformKeyEquivalent]
-[ChromeCommandDispatcherDelegate postPerformKeyEquivalent]

The common feature of all of these functions is that they end up
calling chrome::ExecuteCommand. Add a mojo method to call
chrome::ExecuteCommand and implement it for BrowserFrameMac.

Bug: 895169
Change-Id: Iada42fc24544ca12b8867e54eb1549da9679f6a7
Reviewed-on: https://chromium-review.googlesource.com/c/1359137
Commit-Queue: ccameron <ccameron@chromium.org>
Reviewed-by: Elly Fong-Jones <ellyjones@chromium.org>
Reviewed-by: Robert Sesek <rsesek@chromium.org>
Cr-Commit-Position: refs/heads/master@{#613826}
9 files changed