feat(chromium): roll Chromium to r608752 (#3555)

This roll includes:
- https://crrev.com/608658 - DevTools: emit "init" lifecycle event when document gets opened

References #728

package.json

@@ -8,7 +8,7 @@
     "node": ">=6.4.0"
   },
   "puppeteer": {
-    "chromium_revision": "606647"
+    "chromium_revision": "608752"
   },
   "scripts": {
     "unit": "node test/test.js",