Only use createElement for HTML.

Fix #2737. The previous fix for #2722 meant that createElement was used to
create HTML elements in HTML documents, but it also meant it was used to create
SVG elements in SVG documents, which failed: createElement only inherits the
namespace in HTML documents, not in other document types.

https://www.w3.org/TR/dom/#dom-document-createelement

d3.js

@@ -1,6 +1,6 @@
 !function() {
   var d3 = {
-    version: "3.5.15"
+    version: "3.5.16"
   };
   var d3_arraySlice = [].slice, d3_array = function(list) {
     return d3_arraySlice.call(list);
@@ -620,9 +620,10 @@
       return d3_selectAll(selector, this);
     };
   }
+  var d3_nsXhtml = "http://www.w3.org/1999/xhtml";
   var d3_nsPrefix = {
     svg: "http://www.w3.org/2000/svg",
-    xhtml: "http://www.w3.org/1999/xhtml",
+    xhtml: d3_nsXhtml,
     xlink: "http://www.w3.org/1999/xlink",
     xml: "http://www.w3.org/XML/1998/namespace",
     xmlns: "http://www.w3.org/2000/xmlns/"
@@ -805,7 +806,7 @@
   function d3_selection_creator(name) {
     function create() {
       var document = this.ownerDocument, namespace = this.namespaceURI;
-      return namespace && namespace !== document.documentElement.namespaceURI ? document.createElementNS(namespace, name) : document.createElement(name);
+      return namespace === d3_nsXhtml && document.documentElement.namespaceURI === d3_nsXhtml ? document.createElement(name) : document.createElementNS(namespace, name);
     }
     function createNS() {
       return this.ownerDocument.createElementNS(name.space, name.local);

package.js

@@ -3,7 +3,7 @@
 Package.describe({
   name: "d3js:d3", // http://atmospherejs.com/d3js/d3
   summary: "D3 (official): A JavaScript visualization library for HTML and SVG.",
-  version: "3.5.15",
+  version: "3.5.16",
   git: "https://github.com/mbostock/d3.git"
 });
 

package.json

@@ -1,6 +1,6 @@
 {
   "name": "d3",
-  "version": "3.5.15",
+  "version": "3.5.16",
   "description": "A JavaScript visualization library for HTML and SVG.",
   "keywords": [
     "dom",

src/core/ns.js

@@ -1,6 +1,8 @@
+var d3_nsXhtml = "http://www.w3.org/1999/xhtml";
+
 var d3_nsPrefix = {
   svg: "http://www.w3.org/2000/svg",
-  xhtml: "http://www.w3.org/1999/xhtml",
+  xhtml: d3_nsXhtml,
   xlink: "http://www.w3.org/1999/xlink",
   xml: "http://www.w3.org/XML/1998/namespace",
   xmlns: "http://www.w3.org/2000/xmlns/"

src/selection/append.js

@@ -13,9 +13,9 @@ function d3_selection_creator(name) {
   function create() {
     var document = this.ownerDocument,
         namespace = this.namespaceURI;
-    return namespace && namespace !== document.documentElement.namespaceURI
-        ? document.createElementNS(namespace, name)
-        : document.createElement(name);
+    return namespace === d3_nsXhtml && document.documentElement.namespaceURI === d3_nsXhtml
+        ? document.createElement(name)
+        : document.createElementNS(namespace, name);
   }
 
   function createNS() {

src/start.js

@@ -1,2 +1,2 @@
 !function(){
-  var d3 = {version: "3.5.15"}; // semver
+  var d3 = {version: "3.5.16"}; // semver