--- a/dom/svg/SVGCircleElement.cpp
+++ b/dom/svg/SVGCircleElement.cpp
@@ -19,19 +19,19 @@ namespace dom {
 JSObject*
 SVGCircleElement::WrapNode(JSContext *aCx, JS::Handle<JSObject*> aGivenProto)
 {
   return SVGCircleElementBinding::Wrap(aCx, this, aGivenProto);
 }
 
 nsSVGElement::LengthInfo SVGCircleElement::sLengthInfo[3] =
 {
-  { &nsGkAtoms::cx, 0, nsIDOMSVGLength::SVG_LENGTHTYPE_NUMBER, SVGContentUtils::X },
-  { &nsGkAtoms::cy, 0, nsIDOMSVGLength::SVG_LENGTHTYPE_NUMBER, SVGContentUtils::Y },
-  { &nsGkAtoms::r, 0, nsIDOMSVGLength::SVG_LENGTHTYPE_NUMBER, SVGContentUtils::XY }
+  { &nsGkAtoms::cx, 0, nsIDOMSVGLength::SVG_LENGTHTYPE_NUMBER, SVGContentUtils::X, true},
+  { &nsGkAtoms::cy, 0, nsIDOMSVGLength::SVG_LENGTHTYPE_NUMBER, SVGContentUtils::Y, true},
+  { &nsGkAtoms::r, 0, nsIDOMSVGLength::SVG_LENGTHTYPE_NUMBER, SVGContentUtils::XY, false}
 };
 
 //----------------------------------------------------------------------
 // Implementation
 
 SVGCircleElement::SVGCircleElement(already_AddRefed<mozilla::dom::NodeInfo>& aNodeInfo)
   : SVGCircleElementBase(aNodeInfo)
 {

--- a/dom/svg/SVGImageElement.cpp
+++ b/dom/svg/SVGImageElement.cpp
@@ -27,20 +27,20 @@ namespace dom {
 JSObject*
 SVGImageElement::WrapNode(JSContext *aCx, JS::Handle<JSObject*> aGivenProto)
 {
   return SVGImageElementBinding::Wrap(aCx, this, aGivenProto);
 }
 
 nsSVGElement::LengthInfo SVGImageElement::sLengthInfo[4] =
 {
-  { &nsGkAtoms::x, 0, nsIDOMSVGLength::SVG_LENGTHTYPE_NUMBER, SVGContentUtils::X },
-  { &nsGkAtoms::y, 0, nsIDOMSVGLength::SVG_LENGTHTYPE_NUMBER, SVGContentUtils::Y },
-  { &nsGkAtoms::width, 0, nsIDOMSVGLength::SVG_LENGTHTYPE_NUMBER, SVGContentUtils::X },
-  { &nsGkAtoms::height, 0, nsIDOMSVGLength::SVG_LENGTHTYPE_NUMBER, SVGContentUtils::Y },
+  { &nsGkAtoms::x, 0, nsIDOMSVGLength::SVG_LENGTHTYPE_NUMBER, SVGContentUtils::X, true},
+  { &nsGkAtoms::y, 0, nsIDOMSVGLength::SVG_LENGTHTYPE_NUMBER, SVGContentUtils::Y, true},
+  { &nsGkAtoms::width, 0, nsIDOMSVGLength::SVG_LENGTHTYPE_NUMBER, SVGContentUtils::X, false},
+  { &nsGkAtoms::height, 0, nsIDOMSVGLength::SVG_LENGTHTYPE_NUMBER, SVGContentUtils::Y, false},
 };
 
 nsSVGElement::StringInfo SVGImageElement::sStringInfo[2] =
 {
   { &nsGkAtoms::href, kNameSpaceID_None, true },
   { &nsGkAtoms::href, kNameSpaceID_XLink, true }
 };
 

--- a/dom/svg/SVGRectElement.cpp
+++ b/dom/svg/SVGRectElement.cpp
@@ -25,22 +25,22 @@ class SVGAnimatedLength;
 JSObject*
 SVGRectElement::WrapNode(JSContext *aCx, JS::Handle<JSObject*> aGivenProto)
 {
   return SVGRectElementBinding::Wrap(aCx, this, aGivenProto);
 }
 
 nsSVGElement::LengthInfo SVGRectElement::sLengthInfo[6] =
 {
-  { &nsGkAtoms::x, 0, nsIDOMSVGLength::SVG_LENGTHTYPE_NUMBER, SVGContentUtils::X },
-  { &nsGkAtoms::y, 0, nsIDOMSVGLength::SVG_LENGTHTYPE_NUMBER, SVGContentUtils::Y },
-  { &nsGkAtoms::width, 0, nsIDOMSVGLength::SVG_LENGTHTYPE_NUMBER, SVGContentUtils::X },
-  { &nsGkAtoms::height, 0, nsIDOMSVGLength::SVG_LENGTHTYPE_NUMBER, SVGContentUtils::Y },
-  { &nsGkAtoms::rx, 0, nsIDOMSVGLength::SVG_LENGTHTYPE_NUMBER, SVGContentUtils::X },
-  { &nsGkAtoms::ry, 0, nsIDOMSVGLength::SVG_LENGTHTYPE_NUMBER, SVGContentUtils::Y }
+  { &nsGkAtoms::x, 0, nsIDOMSVGLength::SVG_LENGTHTYPE_NUMBER, SVGContentUtils::X, true },
+  { &nsGkAtoms::y, 0, nsIDOMSVGLength::SVG_LENGTHTYPE_NUMBER, SVGContentUtils::Y, true },
+  { &nsGkAtoms::width, 0, nsIDOMSVGLength::SVG_LENGTHTYPE_NUMBER, SVGContentUtils::X, false},
+  { &nsGkAtoms::height, 0, nsIDOMSVGLength::SVG_LENGTHTYPE_NUMBER, SVGContentUtils::Y, false},
+  { &nsGkAtoms::rx, 0, nsIDOMSVGLength::SVG_LENGTHTYPE_NUMBER, SVGContentUtils::X, false},
+  { &nsGkAtoms::ry, 0, nsIDOMSVGLength::SVG_LENGTHTYPE_NUMBER, SVGContentUtils::Y, false}
 };
 
 //----------------------------------------------------------------------
 // Implementation
 
 SVGRectElement::SVGRectElement(already_AddRefed<mozilla::dom::NodeInfo>& aNodeInfo)
   : SVGRectElementBase(aNodeInfo)
 {

--- a/dom/svg/nsSVGElement.cpp
+++ b/dom/svg/nsSVGElement.cpp
@@ -1669,20 +1669,24 @@ nsSVGElement::GetAnimatedLengthValues(fl
   while (f && i < info.mLengthCount) {
     uint8_t type = info.mLengths[i].GetSpecifiedUnitType();
     if (!ctx) {
       if (type != nsIDOMSVGLength::SVG_LENGTHTYPE_NUMBER &&
           type != nsIDOMSVGLength::SVG_LENGTHTYPE_PX)
         ctx = GetCtx();
     }
     if (type == nsIDOMSVGLength::SVG_LENGTHTYPE_EMS ||
-        type == nsIDOMSVGLength::SVG_LENGTHTYPE_EXS)
-      *f = info.mLengths[i++].GetAnimValue(this);
-    else
-      *f = info.mLengths[i++].GetAnimValue(ctx);
+        type == nsIDOMSVGLength::SVG_LENGTHTYPE_EXS) {
+      *f = info.mLengths[i].GetAnimValue(this);
+    } else {
+      *f = info.mLengths[i].GetAnimValue(ctx);
+    }
+    if (!info.mLengthInfo[i++].mCanBeNegative && *f < 0) {
+      *f = 0;
+    }
     f = va_arg(args, float*);
   }
 
   va_end(args);
 }
 
 nsSVGElement::LengthListAttributesInfo
 nsSVGElement::GetLengthListInfo()

--- a/dom/svg/nsSVGElement.h
+++ b/dom/svg/nsSVGElement.h
@@ -367,16 +367,17 @@ protected:
 
   static nsIAtom* GetEventNameForAttr(nsIAtom* aAttr);
 
   struct LengthInfo {
     nsIAtom** mName;
     float     mDefaultValue;
     uint8_t   mDefaultUnitType;
     uint8_t   mCtxType;
+    bool      mCanBeNegative;
   };
 
   struct LengthAttributesInfo {
     nsSVGLength2* mLengths;
     LengthInfo*   mLengthInfo;
     uint32_t      mLengthCount;
 
     LengthAttributesInfo(nsSVGLength2 *aLengths,