Update DRACOLoader and draco_decoder.

Adds isVersionSupported() method.

examples/js/loaders/DRACOLoader.js

@@ -44,18 +44,8 @@ THREE.DRACOLoader.prototype = {
         this.verbosity = level;
     },
 
-    decodeDracoFile: ( function() {
-        let dracoDecoder;
-
-        if (typeof DracoModule === 'function') {
-          dracoDecoder = DracoModule();
-        } else {
-          console.error('THREE.DRACOLoader: DracoModule not found.');
-          return;
-        }
-
-        return function(rawBuffer) {
-          const scope = this;
+    decodeDracoFile: function(rawBuffer) {
+      const dracoDecoder = THREE.DRACOLoader.getDecoder();
       /*
        * Here is how to use Draco Javascript decoder and get the geometry.
        */
@@ -80,13 +70,11 @@ THREE.DRACOLoader.prototype = {
         console.error(errorMsg);
         throw new Error(errorMsg);
       }
-          return scope.convertDracoGeometryTo3JS(wrapper, geometryType, buffer,
-                                                 dracoDecoder);
-        }
-    } )(),
+      return this.convertDracoGeometryTo3JS(wrapper, geometryType, buffer);
+    },
 
-    convertDracoGeometryTo3JS: function(wrapper, geometryType, buffer,
-                                        dracoDecoder) {
+    convertDracoGeometryTo3JS: function(wrapper, geometryType, buffer) {
+        const dracoDecoder = THREE.DRACOLoader.getDecoder();
         let dracoGeometry;
         const start_time = performance.now();
         if (geometryType == dracoDecoder.TRIANGULAR_MESH) {
@@ -273,5 +261,28 @@ THREE.DRACOLoader.prototype = {
           console.log('Import time: ' + this.import_time);
         }
         return geometry;
+    },
+
+    isVersionSupported: function(version) {
+        return THREE.DRACOLoader.getDecoder().isVersionSupported(version);
     }
 };
+
+/**
+ * Returns a singleton instance of the DracoModule decoder. Creating multiple
+ * copies of the decoder is expensive.
+ */
+THREE.DRACOLoader.getDecoder = (function() {
+    let decoder;
+
+    return function() {
+        if (typeof DracoModule === 'undefined') {
+          throw new Error('THREE.DRACOLoader: DracoModule not found.');
+        }
+
+        decoder = decoder || DracoModule();
+
+        return decoder;
+    };
+
+})();