Add JSON serializers

Fixes http://www.w3.org/mid/546B713E.6040806@mit.edu

Author: zcorpan

geometry/Overview.bs

@@ -68,6 +68,8 @@ interface DOMPointReadOnly {
     readonly attribute unrestricted double w;
 
     DOMPoint matrixTransform(optional DOMMatrixInit matrix);
+
+    serializer = { attribute };
 };
 
 [Constructor(optional unrestricted double x = 0, optional unrestricted double y = 0,
@@ -189,6 +191,8 @@ interface DOMRectReadOnly {
     readonly attribute unrestricted double right;
     readonly attribute unrestricted double bottom;
     readonly attribute unrestricted double left;
+
+    serializer = { attribute };
 };
 
 [Constructor(optional unrestricted double x = 0, optional unrestricted double y = 0,
@@ -273,6 +277,8 @@ interface DOMQuad {
     [SameObject] readonly attribute DOMPoint p3;
     [SameObject] readonly attribute DOMPoint p4;
     [NewObject] DOMRect getBounds();
+
+    serializer = { attribute };
 };
 
 dictionary DOMQuadInit {
@@ -468,6 +474,7 @@ interface DOMMatrixReadOnly {
     Float32Array        toFloat32Array();
     Float64Array        toFloat64Array();
                         stringifier;
+                        serializer = [ m11, m12, m13, m14, m21, m22, m23, m24, m31, m32, m33, m34, m41, m42, m43, m44 ];
 };
 
 [Constructor(sequence<unrestricted double> numberSequence),