Add CanMinimize to classes that implement WidgetDelegate::CanMaximize.

There were some cases where we use CanMaximize to determine if
minimization should be disabled. They now use CanMinimize:
- custom_frame_view_ash
- hwnd_message_handler

All classes that implement CanMaximize now implement
CanMinimize in the same way, so there should no change in
behavior.

BUG=328241,341010

Review URL: https://codereview.chromium.org/583603004

Cr-Commit-Position: refs/heads/master@{#296381}
29 files changed