Make SVGTextContentElement methods behave consistently with Firefox and IE

Source/core/svg/SVGTextContentElement.idl

Index: Source/core/svg/SVGTextContentElement.idl
diff --git a/Source/core/svg/SVGTextContentElement.idl b/Source/core/svg/SVGTextContentElement.idl
index 4d693752940fa68791c716e901f1c1ee9d4834bf..f4ce37dc97d960d38f451364a82b9e4c5327c245 100644
--- a/Source/core/svg/SVGTextContentElement.idl
+++ b/Source/core/svg/SVGTextContentElement.idl
@@ -34,15 +34,13 @@ interface SVGTextContentElement : SVGGraphicsElement {
 
     long getNumberOfChars();
     float getComputedTextLength();
-    [RaisesException] float getSubStringLength([Default=Undefined,IsIndex] optional unsigned long offset,
-                             [Default=Undefined,IsIndex] optional unsigned long length);
-    [RaisesException] SVGPoint getStartPositionOfChar([Default=Undefined,IsIndex] optional unsigned long offset);
-    [RaisesException] SVGPoint getEndPositionOfChar([Default=Undefined,IsIndex] optional unsigned long offset);
-    [RaisesException] SVGRect getExtentOfChar([Default=Undefined,IsIndex] optional unsigned long offset);
-    [RaisesException] float getRotationOfChar([Default=Undefined,IsIndex] optional unsigned long offset);
-    long getCharNumAtPosition([Default=Undefined] optional SVGPoint point);
-    [RaisesException] void selectSubString([Default=Undefined,IsIndex] optional unsigned long offset,
-                         [Default=Undefined,IsIndex] optional unsigned long length);
+    [RaisesException] float getSubStringLength(unsigned long offset, unsigned long length);
+    [RaisesException] SVGPoint getStartPositionOfChar(unsigned long offset);
+    [RaisesException] SVGPoint getEndPositionOfChar(unsigned long offset);
+    [RaisesException] SVGRect getExtentOfChar(unsigned long offset);
+    [RaisesException] float getRotationOfChar(unsigned long offset);
+    long getCharNumAtPosition(SVGPoint point);
+    [RaisesException] void selectSubString(unsigned long offset, unsigned long length);
 };
 
 // FIXME: SVGTextContentElement is not supposed to implement SVGExternalResourcesRequired.