Use Chrome facilities for omnibox state save and restore on Mac.

Use Chrome facilities for omnibox state save and restore on Mac.

TabContents has a facility for storing a bag of stuff across
current-tab changes.  Wire up AutocompleteEditViewMac to use that
facility.  Unfork some code in Browser::TabSelectedAt() so that the
new code gets used, and straighten up the Mac code along the code path
between there and AutocompleteEditViewMac.

This overall change also exposed a couple bugs/mis-features in the
AutocompleteEditViewMac code.

TEST=Text field maintains contents and selection across tab changes, even when edited.

[Scott Hess - ex-Googler, 2009-05-08 20:40:42]

Mike, throwing this to you because your name is all over the relevant cocoa/*.mm
files.

[pink (ping after 24hrs), 2009-05-08 21:18:25]

LGTM, save for the interdependencies i whined about on irc (which I filed for
later cleanup).

http://codereview.chromium.org/114017/diff/1010/2002
File chrome/browser/autocomplete/autocomplete_edit_view_mac.mm (right):

http://codereview.chromium.org/114017/diff/1010/2002#newcode32
Line 32: static PropertyAccessor<AutocompleteEditViewMacState> state;
how does this work with multiple windows if there's only a single accessor? Am i
missing the obvious?

[Scott Hess - ex-Googler, 2009-05-08 22:50:21]

http://codereview.chromium.org/114017/diff/1010/2002
File chrome/browser/autocomplete/autocomplete_edit_view_mac.mm (right):

http://codereview.chromium.org/114017/diff/1010/2002#newcode32
Line 32: static PropertyAccessor<AutocompleteEditViewMacState> state;
On 2009/05/08 21:18:26, pink wrote:
> how does this work with multiple windows if there's only a single accessor? Am
i
> missing the obvious?

Oh, I hope I don't hurt myself, here ... brief summary is "This isn't obvious".

So, I believe that the property bag is a thing which maps unique identifiers to
data.  In this case, the bag itself is held by the TabContents instance.  The
accessor doesn't actually contain the data, it contains the unique identifier. 
SetProperty() on the accessor takes the bag and slots the input under the unique
id.  Similar for GetProperty().

I'm about 93% certain I could code GetStateAccessor() like:
  return *Singleton< PropertyAccessor<AutocompleteEditViewMacState> >::get();
but I'm frankly terrified of what it would mean for me to commit such a thing to
code.

[pink (ping after 24hrs), 2009-05-11 13:50:11]

still lgtm

http://codereview.chromium.org/114017/diff/1010/2002
File chrome/browser/autocomplete/autocomplete_edit_view_mac.mm (right):

http://codereview.chromium.org/114017/diff/1010/2002#newcode32
Line 32: static PropertyAccessor<AutocompleteEditViewMacState> state;
I figured it was something like this. Maybe a comment to this effect? Still
LGTM.