clipboard_mac

Make Mac clipboard code tolerant of nil clipboard without crashing.  Add a
DCHECK to catch this case, and clean up some of the clipboard code.

Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=3051

[Mark Mentovai, 2008-10-08 14:27:22]

Most of the string operations in this file were safe.  Specifically, anything
that goes to one of the three-argument conversion functions is fine, because
those functions just treat zero-length input as an empty string regardless of
input pointer validity.  A couple of the string operations were wrong for input
that might be NULL, which can happen if the pasteboard is nil (or maybe in other
weird cases).  When we cross out of Cocoa/Objective-C, we need to take care and
remember that C++ isn't tolerant of 0 in the same way as Objective-C.

[Avi (use Gerrit), 2008-10-08 14:48:09]

http://codereview.chromium.org/6580/diff/1/2
File base/clipboard_mac.mm (right):

http://codereview.chromium.org/6580/diff/1/2#newcode17
Line 17: NSString* NSStringForWString(const std::wstring& string) {
Can we use sys_string_conversions.h's SysWideToCFStringRef instead of this
version?

[Mark Mentovai, 2008-10-08 19:40:29]

Jeremy's out today.  Avi, you can do the review.

[Avi (use Gerrit), 2008-10-08 20:04:54]

Apart from that, lgtm

http://codereview.chromium.org/6580/diff/202/6
File base/clipboard_mac.mm (right):

http://codereview.chromium.org/6580/diff/202/6#newcode18
Line 18: NSString* NSStringForWString(const std::wstring& string) {
Can we use the SysWideToNSString just added in issue 6355's
sys_string_conversions?