Theme delegate fixes for the 10.6 SDK folllowing r43708....

Theme delegate fixes for the 10.6 SDK folllowing r43708.

In the 10.6 SDK, -[NSWindow delegate] returns id<NSWindowDelegate>, not just
id, and the three selectors used in r43708 are not declared in
NSWindowDelegate.  This results in errors such as "warning: '-themeProvider'
not found in protocol(s)".

Testing the selectors before using them is safe and not incorrect, but you
guys might actually want to make more of an assertion about what it means to
be a ChromeBrowserWindow's or FullscreenWindow's delegate, or perhaps even
a ChromeEventProcessingWindow's delegate.  Alternatively, it may be
appropriate to add a ChromeThemedWindow layer as a subclass of CEPW and
superclass of CBW and FW.  (CEPW's other subclass is InfoBubbleWindow.)

BUG=none
TEST=none

Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=43746

[Mark Mentovai, 2010-04-06 18:16:15]

The patch itself fixes the build error, but I suspect that we might want to
restructure things along the lines of my suggestion in the change description. 
What do you guys think?

[rohitrao (ping after 24h), 2010-04-06 18:52:30]

This was supposed to be a quick fix to get themes working again.  In the long
run, I think a few other things need to happen.

1) We should revisit making a common base class for ChromeBrowserWindow and
FullscreenWindow, especially since it looks like I forgot to copy some other
logic into FullscreenWindow.

2) I need to stop the browser from crashing when I call setWindowController:
earlier in setFullscreen:.

3) Pending the outcome of #2, we should decide if theme-related questions are
jobs for a delegate or a window controller.  To me, they seem more like the job
of a delegate.  In either case, we should still be checking to make sure that
the selectors exist or define a protocol to ensure that they are.

Your changes LGTM for now, especially since the original code really has the
same fundamental issues, just without the SDK complaining.

[Avi (use Gerrit), 2010-04-06 19:38:05]

Code LGTM

I'm not sure another class layer would mean much. After all, it still would have
to dig up some connection to the window controller (unless it had its own copies
of the theme).

I was trying to avoid the -respondsToSelector bit in my code for speed. If you
don't mind the hit...

[Mark Mentovai, 2010-04-06 19:40:16]

The other thing to do would be to assert in the code that the delegate needs to
take a specific form.  See, for example, http://codereview.chromium.org/1550002
from last week.

I wouldn’t want to do that without sticking an intermediate class in there,
though.  Too much heinous stuff duplicated in these classes.