[Mac] Factor out keyboard shortcut handling from ChromeEventProcessingWindow.
This pulls the redispatching logic into CommandDispatcher which allows
it to be reused independent of Chrome, and is a major step towards enabling
keyboard shortcuts in MacViews. By using CommandDispatcher in
NativeWidgetMacNSWindow, main menu key equivalents (e.g. Cmd+c) now
work when the WebContents has focus.
Chrome-specific parts are moved to ChromeCommandDispatcherDelegate,
which will, in future, also be used by the Views browser in mac_views_browser=1
builds.
This includes minor changes to webview_example to demo command redispatch
in non-Chrome Views. E.g. Cmd+q now works in views_examples_with_content_exe
when the webview is focused.
Some test coverage is provided by GlobalKeyboardShortcutsTest.
BUG=508438, 504677
TEST=All keyboard shortcuts continue to work as before.
Review URL: https://codereview.chromium.org/1255783002
Cr-Commit-Position: refs/heads/master@{#346530}
16 files changed
