Run jshint over all JavaScript files

ports/gdb/tests/gdb_background_test.js

Index: ports/gdb/tests/gdb_background_test.js
diff --git a/ports/gdb/tests/gdb_background_test.js b/ports/gdb/tests/gdb_background_test.js
index 9d99a2f9c31ac34ac437108e272c1c0a13f03a3c..75d17538de443c76358b04c696066092ef3cda45 100644
--- a/ports/gdb/tests/gdb_background_test.js
+++ b/ports/gdb/tests/gdb_background_test.js
@@ -4,6 +4,10 @@
  * found in the LICENSE file.
  */
 
+/* globals ASSERT_EQ, ASSERT_LE, ASSERT_GE, EXPECT_EQ, TEST_F, TEST */
+/* globals chrometest, TestModuleTest, waitForExtraModuleCount */
+/* globals waitIgnoringTerminal */
+
 'use strict';
 
 function GdbExtensionTestModuleTest() {
@@ -125,7 +129,7 @@ GdbExtensionTestModuleTest.prototype.waitForGdbPrompt = function(min, max) {
 GdbExtensionTestModuleTest.prototype.waitForGdbReply = function(lines) {
   var self = this;
   function checkLine() {
-    if (lines.length == 0) {
+    if (lines.length === 0) {
       return;
     }
     return Promise.resolve().then(function() {