Adjust the brace-style ESLint rule to disallow single lines (and also enable no-iterator)

See http://eslint.org/docs/rules/brace-style.
Having the opening/closing braces on the same line can often make the code slightly more difficult to read, in particular for `if`/`else if` statements, compared to using new lines.

This patch also, for consistency with `mozilla-central`, enables the [`no-iterator`](http://eslint.org/docs/rules/no-iterator) rule. Note that this rule didn't require a single code change.

src/core/worker.js

@@ -94,7 +94,9 @@ IPDFStream.prototype = {
    * Gets a reader for the entire PDF data.
    * @returns {IPDFStreamReader}
    */
-  getFullReader: function () { return null; },
+  getFullReader: function () {
+    return null;
+  },
 
   /**
    * Gets a reader for the range of the PDF data.
@@ -102,7 +104,9 @@ IPDFStream.prototype = {
    * @param {number} end - the end offset of the data.
    * @returns {IPDFStreamRangeReader}
    */
-  getRangeReader: function (begin, end) { return null; },
+  getRangeReader: function (begin, end) {
+    return null;
+  },
 
   /**
    * Cancels all opened reader and closes all their opened requests.
@@ -123,14 +127,18 @@ IPDFStreamReader.prototype = {
    * the PDF data stream are available.
    * @returns {Promise}
    */
-  get headersReady() { return null; },
+  get headersReady() {
+    return null;
+  },
 
   /**
    * Gets PDF binary data length. It is defined after the headersReady promise
    * is resolved.
    * @returns {number} The data length (or 0 if unknown).
    */
-  get contentLength() { return 0; },
+  get contentLength() {
+    return 0;
+  },
 
   /**
    * Gets ability of the stream to handle range requests. It is defined after
@@ -138,14 +146,18 @@ IPDFStreamReader.prototype = {
    * or an error occurs.
    * @returns {boolean}
    */
-  get isRangeSupported() { return false; },
+  get isRangeSupported() {
+    return false;
+  },
 
   /**
    * Gets ability of the stream to progressively load binary data. It is defined
    * after the headersReady promise is resolved.
    * @returns {boolean}
    */
-  get isStreamingSupported() { return false; },
+  get isStreamingSupported() {
+    return false;
+  },
 
   /**
    * Requests a chunk of the binary data. The method returns the promise, which
@@ -183,7 +195,9 @@ IPDFStreamRangeReader.prototype = {
    * Gets ability of the stream to progressively load binary data.
    * @returns {boolean}
    */
-  get isStreamingSupported() { return false; },
+  get isStreamingSupported() {
+    return false;
+  },
 
   /**
    * Requests a chunk of the binary data. The method returns the promise, which