Attempting to browse the NewProgressBar.cs changeset with a File
Contents Browser, I got the following error:

PseudoClass(Object)>>doesNotUnderstand: #inheritsFrom:
	Receiver: a PseudoClass(#NewProgressMorph)
	Arguments and temporary variables: 
		aMessage: 	inheritsFrom: TestCase
	Receiver's instance variables: 
		name: 	#NewProgressMorph
		definition: 	'RectangleMorph subclass: #NewProgressMorph
	instanceVariableNames:...etc...
		organization: 	('initialization' done: initialize setDefaultParameters
updateCol...etc...
		source: 	a Dictionary(#done:->a ChangeRecord #freeSlot:->a
ChangeRecord #initial...etc...
		metaClass: 	a PseudoMetaclass(#NewProgressMorph)

FileContentsBrowser(Browser)>>isTestCase:
	Receiver: a FileContentsBrowser
	Arguments and temporary variables: 
		aClass: 	a PseudoClass(#NewProgressMorph)
	Receiver's instance variables: 
		dependents: 	#(a SystemWindow(3088) a PluggableListMorph(3418) a
PluggableListMo...etc...
		contents: 	nil
		currentCompiledMethod: 	nil
		contentsSymbol: 	#showDiffs
		systemOrganizer: 	('NewProgressBar.cs' NewProgressBarMorph
NewProgressMorph Prog...etc...
		classOrganizer: 	('initialization' done: initialize
setDefaultParameters updateC...etc...
		metaClassOrganizer: 	('instance creation' done: label:min:max: new)
('class init...etc...
		systemCategoryListIndex: 	1
		classListIndex: 	2
		messageCategoryListIndex: 	0
		messageListIndex: 	0
		editSelection: 	#editClass
		metaClassIndicated: 	false
		packages: 	a Dictionary('NewProgressBar.cs'->a FilePackage )
		infoString: 	nil

FileContentsBrowser(Browser)>>testClassBrowsed
	Receiver: a FileContentsBrowser
	Arguments and temporary variables: 

	Receiver's instance variables: 
		dependents: 	#(a SystemWindow(3088) a PluggableListMorph(3418) a
PluggableListMo...etc...
		contents: 	nil
		currentCompiledMethod: 	nil
		contentsSymbol: 	#showDiffs
		systemOrganizer: 	('NewProgressBar.cs' NewProgressBarMorph
NewProgressMorph Prog...etc...
		classOrganizer: 	('initialization' done: initialize
setDefaultParameters updateC...etc...
		metaClassOrganizer: 	('instance creation' done: label:min:max: new)
('class init...etc...
		systemCategoryListIndex: 	1
		classListIndex: 	2
		messageCategoryListIndex: 	0
		messageListIndex: 	0
		editSelection: 	#editClass
		metaClassIndicated: 	false
		packages: 	a Dictionary('NewProgressBar.cs'->a FilePackage )
		infoString: 	nil

PluggableButtonMorph>>getModelState
	Receiver: a PluggableButtonMorph(633)
	Arguments and temporary variables: 

	Receiver's instance variables: 
		bounds: 	808 at 241 corner: 851 at 265
		owner: 	an AlignmentMorph(2326)
		submorphs: 	#(an AlignmentMorph(2733))
		fullBounds: 	808 at 241 corner: 851 at 265
		color: 	(Color r: 0.953 g: 0.953 b: 0.884)
		extension: 	a MorphExtension (3778) [balloonText]  [other: 
(layoutPolicy -> a TableLayout) (layoutProperties -> a
TableLayoutProperties)]...etc...
		borderWidth: 	0
		borderColor: 	Color black
		model: 	a FileContentsBrowser
		label: 	'test'
		getStateSelector: 	#testClassBrowsed
		actionSelector: 	#browseTestClass
		getLabelSelector: 	nil
		getMenuSelector: 	nil
		shortcutCharacter: 	nil
		askBeforeChanging: 	true
		triggerOnMouseDown: 	false
		offColor: 	(Color r: 0.953 g: 0.953 b: 0.884)
		onColor: 	(Color r: 0.804 g: 0.804 b: 0.745)
		feedbackColor: 	Color red
		showSelectionFeedback: 	false
		allButtons: 	nil
		arguments: 	nil
		argumentsProvider: 	nil
		argumentsSelector: 	nil


--- The full stack ---
PseudoClass(Object)>>doesNotUnderstand: #inheritsFrom:
FileContentsBrowser(Browser)>>isTestCase:
FileContentsBrowser(Browser)>>testClassBrowsed
PluggableButtonMorph>>getModelState
 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
PluggableButtonMorph>>update:
[] in FileContentsBrowser(Object)>>changed: {[:aDependent | aDependent
update: aParameter]}
DependentsArray>>do:
FileContentsBrowser(Object)>>changed:
FileContentsBrowser(Browser)>>editSelection:
FileContentsBrowser(Browser)>>classListIndex:
PluggableListMorph>>changeModelSelection:
PluggableListMorph>>mouseUp:
PluggableListMorph(Morph)>>handleMouseUp:
MouseButtonEvent>>sentTo:
PluggableListMorph(Morph)>>handleEvent:
...etc...