Overhaul omnibox focus detection on Mac.

Overhaul omnibox focus detection on Mac.

Rather than aiming to detect acquisition and loss of focus in
|field_|, just acknowledge that there are cases where |field_| has
focus but |model_| doesn't know.  If |field_| has focus but no editing
has been done, then |model_| will take no action, so this is
reasonable.

Window resigning key just closes the popup, and doesn't affect
|model_| focus.  Thus, there is no need to deal with acquiring focus
when the window becomes key again, and we can live fine within the
constraints of -*DidBeginEditing: and -*ShouldEndEditing:.

Added checks for |field_| being focussed in all the relevant places.

http://crbug.com/12338

[Scott Hess - ex-Googler, 2009-05-21 23:42:06]

I think this is good to go, but I need to step back and think about it a bit. 
Seems like a reasonable time for someone else to comment.

[pink (ping after 24hrs), 2009-05-22 13:09:28]

LGTM

http://codereview.chromium.org/113746/diff/1/2
File chrome/browser/autocomplete/autocomplete_edit_view_mac.h (right):

http://codereview.chromium.org/113746/diff/1/2#newcode90
Line 90: void OnDidBeginEditing();
if it comes before anything is communicated to the model, should it be called
OnWillBeginEditing()? *shrug*

http://codereview.chromium.org/113746/diff/1/3
File chrome/browser/autocomplete/autocomplete_edit_view_mac.mm (right):

http://codereview.chromium.org/113746/diff/1/3#newcode478
Line 478: // can detect that without subclassing NSTextField.
Can you can get [NSEvent currentEvent] and check for the control key?

[Scott Hess - ex-Googler, 2009-05-22 17:15:20]

Also added some commentary around focus handling.

http://codereview.chromium.org/113746/diff/1/2
File chrome/browser/autocomplete/autocomplete_edit_view_mac.h (right):

http://codereview.chromium.org/113746/diff/1/2#newcode90
Line 90: void OnDidBeginEditing();
On 2009/05/22 13:09:28, pink wrote:
> if it comes before anything is communicated to the model, should it be called
> OnWillBeginEditing()? *shrug*

Was named after the ObjC method, -controlTextDidBeginEditing:.  Seems like a
tossup, but Will does seem closer to the intent, so Done.

http://codereview.chromium.org/113746/diff/1/3
File chrome/browser/autocomplete/autocomplete_edit_view_mac.mm (right):

http://codereview.chromium.org/113746/diff/1/3#newcode478
Line 478: // can detect that without subclassing NSTextField.
On 2009/05/22 13:09:28, pink wrote:
> Can you can get [NSEvent currentEvent] and check for the control key?

Definitely could.  For now, I'd rather callout places where it matters, but not
actually address it, because I don't think the modifications Control makes to
autocomplete are probably MacDev material.

On Windows results change on depress/release of Control, not on the next input. 
So I think that really implementing that feature will require more than what I
can intercept in a target/delegate type object.