Fixup 41caf2d for DeltaValue tables

Not that I can find any fonts having these... Had to construct one
to test.
diff --git a/Lib/fontTools/ttLib/tables/otBase.py b/Lib/fontTools/ttLib/tables/otBase.py
index e6fd0ab..43123f1 100644
--- a/Lib/fontTools/ttLib/tables/otBase.py
+++ b/Lib/fontTools/ttLib/tables/otBase.py
@@ -555,7 +555,7 @@
 
 			else:
 				table[conv.name] = conv.read(reader, font, countVars)
-				if conv.isCount:
+				if conv.isCount or conv.isSize:
 					counts.append(conv.name)
 					countVars[conv.name] = table[conv.name]
 
@@ -618,6 +618,9 @@
 				countVars[name] = storeValueFactory(table, name)
 			else:
 				conv.write(writer, font, countVars, value)
+				if conv.isSize:
+					countVars[conv.name] = value
+					counts.append(conv.name)
 
 		for count in counts:
 			del countVars[count]
diff --git a/Lib/fontTools/ttLib/tables/otConverters.py b/Lib/fontTools/ttLib/tables/otConverters.py
index 240979b..ba8c61a 100644
--- a/Lib/fontTools/ttLib/tables/otConverters.py
+++ b/Lib/fontTools/ttLib/tables/otConverters.py
@@ -49,6 +49,7 @@
 		self.repeatOffset = repeatOffset
 		self.tableClass = tableClass
 		self.isCount = name.endswith("Count")
+		self.isSize = name.endswith("Size") or name=="DeltaFormat"
 	
 	def read(self, reader, font, countVars):
 		"""Read a value from the reader."""
@@ -290,10 +291,9 @@
 class DeltaValue(BaseConverter):
 	
 	def read(self, reader, font, countVars):
-		table = countVars.getTop()
-		StartSize = table["StartSize"]
-		EndSize = table["EndSize"]
-		DeltaFormat = table["DeltaFormat"]
+		StartSize = countVars["StartSize"]
+		EndSize = countVars["EndSize"]
+		DeltaFormat = countVars["DeltaFormat"]
 		assert DeltaFormat in (1, 2, 3), "illegal DeltaFormat"
 		nItems = EndSize - StartSize + 1
 		nBits = 1 << DeltaFormat
@@ -314,11 +314,10 @@
 		return DeltaValue
 	
 	def write(self, writer, font, countVars, value, repeatIndex=None):
-		table = countVars.getTop()
-		StartSize = table["StartSize"]
-		EndSize = table["EndSize"]
-		DeltaFormat = table["DeltaFormat"]
-		DeltaValue = table["DeltaValue"]
+		StartSize = countVars["StartSize"]
+		EndSize = countVars["EndSize"]
+		DeltaFormat = countVars["DeltaFormat"]
+		DeltaValue = value
 		assert DeltaFormat in (1, 2, 3), "illegal DeltaFormat"
 		nItems = EndSize - StartSize + 1
 		nBits = 1 << DeltaFormat