Increase Bind/Callback Arity from 6 -> 7.

Increase Bind/Callback Arity from 6 -> 7.

A few functions need this and the expected compile-speed impact is low.  We should be careful when raising this number higher.  If you're binding a function that has more parameters than this supports, consider refactoring your API to use a parameter struct or something.

Template equation: (n^2 + 26n) / 2
Template growth: 96 -> 116 types.

BUG=98542
TEST=try bots

Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=111788

[willchan no longer on Chromium, 2011-11-28 20:02:49]

lgtm

http://codereview.chromium.org/8728010/diff/1/base/bind.h.pump
File base/bind.h.pump (right):

http://codereview.chromium.org/8728010/diff/1/base/bind.h.pump#newcode8
base/bind.h.pump:8: $var MAX_ARITY = 7
It'd be great to add a comment explaining the pros/cons here and stating that
the number chosen was a result of the tradeoff. Maybe have the other files point
to the comment here.

[awong, 2011-11-28 20:16:38]

Added comments, and removed one stale comment.

http://codereview.chromium.org/8728010/diff/4001/base/bind_internal.h
File base/bind_internal.h (left):

http://codereview.chromium.org/8728010/diff/4001/base/bind_internal.h#oldcode11
base/bind_internal.h:11: // Do we want to allow creating a fully unbound
method??
Stale TODO. I thought this through and realized that our normal enforcement that
refcounted parameters need to take a scoped_refptr already handles this... 
Assume Foo is refcounted.

Callback<void(Foo*)> cb = Bind(&Foo::VoidFunc);

Bind(cb, new Foo());  // Compile failure since you're binding a Foo*.

So yay! All works!