Make sure that Clipboard operations that require dispatching...

Make sure that Clipboard operations that require dispatching
of windows messages are performed on the UI thread.

SetClipboardData requires the clipboard to be open with a handle
to a window that will be notified when the contents are going to
change again. If Windows messages are not processed, any other app
writing to the clipboard will be locked while we acknowledge their
request (by processing the message).

The IO thread doesn't pump windows messages anymore so write
clipboard operations cannot be performed from that thread and have
to be posted to another thread.

BUG=5823
Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=9003

[jam, 2009-01-31 00:24:47]

lgtm

http://codereview.chromium.org/19733/diff/1/4
File base/clipboard.h (right):

http://codereview.chromium.org/19733/diff/1/4#newcode190
Line 190: // true if we can create a window.
nit: please capitalize True.