Instrumenting tools/doc/html.js for performance analysis

html.diff

diff --git a/tools/doc/html.js b/tools/doc/html.js
index 974eab769c..b4153c4eee 100644
--- a/tools/doc/html.js
+++ b/tools/doc/html.js
@@ -53,6 +53,8 @@ function navClasses() {
   }
 }
 
+let start = new Date().getTime();
+
 const gtocPath = path.join(docPath, 'api', '_toc.md');
 const gtocMD = fs.readFileSync(gtocPath, 'utf8').replace(/^@\/\/.*$/gm, '');
 const gtocHTML = unified()
@@ -63,23 +65,46 @@ const gtocHTML = unified()
   .use(html)
   .processSync(gtocMD).toString();
 
+const gtoc_time = new Date().getTime();
+let times = {gtoc: gtoc_time - start};
+start = gtoc_time;
+
 const templatePath = path.join(docPath, 'template.html');
 const template = fs.readFileSync(templatePath, 'utf8');
 
+function timestamp({ name }) {
+  return (tree, file) => {
+    const ts = new Date().getTime();
+    times[name] = ts - start;
+    start = ts;
+  }
+}
+
 function toHTML({ input, filename, nodeVersion, analytics }, cb) {
   filename = path.basename(filename, '.md');
 
   const content = unified()
     .use(markdown)
+    .use(timestamp.bind({}), { name : 'parse' })
     .use(firstHeader)
+    .use(timestamp.bind({}), { name : 'firstHeader' })
     .use(preprocessText)
+    .use(timestamp.bind({}), { name : 'preprocessText' })
     .use(preprocessElements, { filename: filename })
+    .use(timestamp.bind({}), { name : 'preprocessElements' })
     .use(buildToc, { filename: filename })
+    .use(timestamp.bind({}), { name : 'buildToc' })
     .use(remark2rehype, { allowDangerousHTML: true })
+    .use(timestamp.bind({}), { name : 'remark2rehype' })
     .use(raw)
+    .use(timestamp.bind({}), { name : 'raw' })
     .use(html)
     .processSync(input);
 
+times.serialize = new Date().getTime() - start;
+
+console.error(times);
+
   const id = filename.replace(/\W+/g, '-');
 
   let HTML = template.replace('__ID__', id)