nsIWindowProvider in Firefox 3.6a1pre

 A method to request that this provider provide a window.  The window
 returned need not to have the right name or parent set on it; setting
 those is the caller's responsibility.  The provider can always return null
 to have the caller create a brand-new window.

 @param aParent Must not be null.  This is the window that the caller wants
                to use as the parent for the new window.  Generally,
                nsIWindowProvider implementors can expect to be somehow
                related to aParent; the relationship may depend on the
                nsIWindowProvider implementation.
 @param aChromeFlags The chrome flags the caller will use to create a new
                      window if this provider returns null.  See
                      nsIWebBrowserChrome for the possible values of this
                      field.
 @param aPositionSpecified Whether the attempt to create a window is trying
                           to specify a position for the new window.
 @param aSizeSpecified Whether the attempt to create a window is trying to
                       specify a size for the new window.
 @param aURI The URI to be loaded in the new window.  The nsIWindowProvider
             implementation MUST NOT load this URI in the window it
             returns.  This URI is provided solely to help the
             nsIWindowProvider implenentation make decisions; the caller
             will handle loading the URI in the window returned if
             provideWindow returns a window.  Note that the URI may be null
             if the load cannot be represented by a single URI (e.g. if
             the load has extra load flags, POST data, etc).
 @param aName The name of the window being opened.  Setting the name on the
              return value of provideWindow will be handled by the caller;
              aName is provided solely to help the nsIWindowProvider
              implementation make decisions.
 @param aFeatures The feature string for the window being opened.  This may
                  be empty.  The nsIWindowProvider implementation is
                  allowed to apply the feature string to the window it
                  returns in any way it sees fit.  See the nsIWindowWatcher
                  interface for details on feature strings.
 @param aWindowIsNew [out] Whether the window being returned was just
                           created by the window provider implementation.
                           This can be used by callers to keep track of which
                           windows were opened by the user as opposed to
                           being opened programmatically.  This should be set
                           to false if the window being returned existed
                           before the provideWindow() call.  The value of this
                           out parameter is meaningless if provideWindow()
                           returns null.
 @return A window the caller should use or null if the caller should just
         create a new window.  The returned window may be newly opened by
         the nsIWindowProvider implementation or may be a window that
         already existed.

 @see nsIWindowWatcher for more information on aFeatures.
 @see nsIWebBrowserChrome for more information on aChromeFlags.