DevTools: Fix presubmit scripts on Windows

This fixes a couple presubmit issues when running on Windows:

* check_gn didn't properly normalize paths
* eslint didn't execute in node successfully since the bin style for the
npm install was unix specific (it's a CMD file on Windows)


Bug: 929919
Change-Id: Iec7e1057254047bd0a6539e16df964dc8a58d528
Reviewed-on: https://chromium-review.googlesource.com/c/1459576
Reviewed-by: Dmitry Gozman <dgozman@chromium.org>
Commit-Queue: Jeff Fisher <jeffish@microsoft.com>
Cr-Original-Commit-Position: refs/heads/master@{#633810}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: d2dcac5ced285df053bc094b8e36d80a998f0079
diff --git a/scripts/check_gn.js b/scripts/check_gn.js
index 7b01271..e17ce41 100644
--- a/scripts/check_gn.js
+++ b/scripts/check_gn.js
@@ -73,7 +73,7 @@
   const errors = [];
   const excludedFiles = ['InspectorBackendCommands.js', 'SupportedCSSProperties.js', 'ARIAProperties.js'];
   const gnVariable = 'all_devtools_files';
-  const lines = selectGNLines(`${gnVariable} = [`, ']');
+  const lines = selectGNLines(`${gnVariable} = [`, ']').map(path.normalize);
   if (!lines.length) {
     return [
       'Could not identify all_devtools_files list in gn file',