SVG doesn't recognize rem units

Source/core/svg/SVGLengthTearOff.cpp

Index: Source/core/svg/SVGLengthTearOff.cpp
diff --git a/Source/core/svg/SVGLengthTearOff.cpp b/Source/core/svg/SVGLengthTearOff.cpp
index e43a606269c486143342e911471eff1a46cbf7b6..a05cae5fee686a998d28a8dc9cb00e2e10f4c155 100644
--- a/Source/core/svg/SVGLengthTearOff.cpp
+++ b/Source/core/svg/SVGLengthTearOff.cpp
@@ -55,7 +55,7 @@ inline bool canResolveRelativeUnits(const SVGElement* contextElement)
 
 SVGLengthType SVGLengthTearOff::unitType()
 {
-    return target()->unitType();
+    return hasExposedLengthUnit() ? target()->unitType() : LengthTypeUnknown;
 }
 
 SVGLengthMode SVGLengthTearOff::unitMode()
@@ -108,7 +108,7 @@ void SVGLengthTearOff::setValueInSpecifiedUnits(float value, ExceptionState& es)
 
 String SVGLengthTearOff::valueAsString()
 {
-    return target()->valueAsString();
+    return hasExposedLengthUnit() ? target()->valueAsString() : String::number(0);

[Erik Dahlström (inactive), 2015/03/31 09:20:50]

Not all <length> properties have 0 (with no unit) as the default (lacuna) value,
e.g https://svgwg.org/svg2-draft/pservers.html#RadialGradientElementCXAttribute.

See http://jsfiddle.net/ffwn1k4t/ and http://jsfiddle.net/ffwn1k4t/1/.

It looks like returning 0 here for "unknown" values is what blink used to do, so
it isn't a functional change really. However, I do think that gecko is more
correct in returning "50%" for cx.

[Shanmuga Pandi, 2015/04/01 15:01:37]

Added TODO note. I will work on this issue seperately.

[Erik Dahlström (inactive), 2015/04/02 07:58:40]

Acknowledged.

 }
 
 void SVGLengthTearOff::setValueAsString(const String& str, ExceptionState& es)
@@ -118,7 +118,16 @@ void SVGLengthTearOff::setValueAsString(const String& str, ExceptionState& es)
         return;
     }
 
+    String oldValue = target()->valueAsString();
+
     target()->setValueAsString(str, es);
+
+    if (!es.hadException() && !hasExposedLengthUnit()) {
+        target()->setValueAsString(oldValue, ASSERT_NO_EXCEPTION); // rollback t o old value
+        es.throwDOMException(SyntaxError, "The value provided ('" + str + "') is invalid.");
+        return;
+    }
+
     commitChange();
 }