js: performance improvement for TextDecoder pollyfill

The UTF-8-only encoder/decoder was performing poorly due to inefficient
array manipulation.
Applied changes from the original text-encoding package that reduce
the amount of copying.

Relates to #316

patches/text-encoding-utf-8+1.0.2.patch

@@ -0,0 +1,52 @@
+diff --git a/node_modules/text-encoding-utf-8/lib/encoding.lib.js b/node_modules/text-encoding-utf-8/lib/encoding.lib.js
+index a067c51..05a1954 100644
+--- a/node_modules/text-encoding-utf-8/lib/encoding.lib.js
++++ b/node_modules/text-encoding-utf-8/lib/encoding.lib.js
+@@ -155,6 +155,7 @@ function codePointsToString(code_points) {
+ function Stream(tokens) {
+   /** @type {!Array.<number>} */
+   this.tokens = [].slice.call(tokens);
++  this.tokens.reverse();
+ }
+
+ Stream.prototype = {
+@@ -176,7 +177,7 @@ Stream.prototype = {
+    read: function() {
+     if (!this.tokens.length)
+       return end_of_stream;
+-     return this.tokens.shift();
++     return this.tokens.pop();
+    },
+
+   /**
+@@ -190,9 +191,9 @@ Stream.prototype = {
+     if (Array.isArray(token)) {
+       var tokens = /**@type {!Array.<number>}*/(token);
+       while (tokens.length)
+-        this.tokens.unshift(tokens.pop());
++        this.tokens.push(tokens.pop());
+     } else {
+-      this.tokens.unshift(token);
++      this.tokens.push(token);
+     }
+   },
+
+@@ -207,9 +208,9 @@ Stream.prototype = {
+     if (Array.isArray(token)) {
+       var tokens = /**@type {!Array.<number>}*/(token);
+       while (tokens.length)
+-        this.tokens.push(tokens.shift());
++        this.tokens.unshift(tokens.shift());
+     } else {
+-      this.tokens.push(token);
++      this.tokens.unshift(token);
+     }
+   }
+ };
+@@ -639,4 +640,4 @@ function UTF8Encoder(options) {
+ }
+
+ exports.TextEncoder = TextEncoder;
+-exports.TextDecoder = TextDecoder;
+\ No newline at end of file
++exports.TextDecoder = TextDecoder;

src/js/bundle.js

@@ -8099,6 +8099,7 @@ var require_encoding_lib = __commonJS({
     var end_of_stream = -1;
     function Stream(tokens) {
       this.tokens = [].slice.call(tokens);
+      this.tokens.reverse();
     }
     Stream.prototype = {
       endOfStream: function() {
@@ -8107,24 +8108,24 @@ var require_encoding_lib = __commonJS({
       read: function() {
         if (!this.tokens.length)
           return end_of_stream;
-        return this.tokens.shift();
+        return this.tokens.pop();
       },
       prepend: function(token) {
         if (Array.isArray(token)) {
           var tokens = token;
           while (tokens.length)
-            this.tokens.unshift(tokens.pop());
+            this.tokens.push(tokens.pop());
         } else {
-          this.tokens.unshift(token);
+          this.tokens.push(token);
         }
       },
       push: function(token) {
         if (Array.isArray(token)) {
           var tokens = token;
           while (tokens.length)
-            this.tokens.push(tokens.shift());
+            this.tokens.unshift(tokens.shift());
         } else {
-          this.tokens.push(token);
+          this.tokens.unshift(token);
         }
       }
     };