Add option "--timing" to mesure gitbook performances

lib/parse/parsePagesList.js

@@ -1,5 +1,6 @@
 var Immutable = require('immutable');
 
+var timing = require('../utils/timing');
 var Page = require('../models/page');
 var walkSummary = require('./walkSummary');
 
@@ -14,27 +15,30 @@ function parsePagesList(book) {
     var summary = book.getSummary();
     var map = Immutable.OrderedMap();
 
-    return walkSummary(summary, function(article) {
-        if (!article.isPage()) return;
+    return timing.measure(
+        'parse.listPages',
+        walkSummary(summary, function(article) {
+            if (!article.isPage()) return;
 
-        var filepath = article.getPath();
+            var filepath = article.getPath();
 
-        // Is the page ignored?
-        if (book.isContentFileIgnored(filepath)) return;
+            // Is the page ignored?
+            if (book.isContentFileIgnored(filepath)) return;
 
-        return fs.statFile(filepath)
-        .then(function(file) {
-            map = map.set(
-                filepath,
-                Page.createForFile(file)
-            );
-        }, function() {
-            // file doesn't exist
-        });
-    })
-    .then(function() {
-        return map;
-    });
+            return fs.statFile(filepath)
+            .then(function(file) {
+                map = map.set(
+                    filepath,
+                    Page.createForFile(file)
+                );
+            }, function() {
+                // file doesn't exist
+            });
+        })
+        .then(function() {
+            return map;
+        })
+    );
 }