Change the pageaction_by_content example to use declarativeContent.

chrome/common/extensions/docs/examples/api/pageAction/pageaction_by_content/manifest.json

 {
   "name" : "Page action by content",
   "version" : "1.1",
-  "description" : "Shows a page action for HTML pages containing the word 'sandwich'",
+  "description" : "Shows a page action for HTML pages containing a video",
   "background" : {
-    "scripts": ["background.js"]
+    "scripts": ["background.js"],
+    "persistent": false
   },
   "page_action" :
   {
-    "default_icon" : "sandwich-19.png",
-    "default_title" : "There's a 'sandwich' in this page!"
+    "default_icon" : "video-19.png",
+    "default_title" : "There's a <video> in this page!"
   },
-  "content_scripts" : [
-    {
-      "matches" : [
-        "http://*/*",
-        "https://*/*"
-      ],
-      "js" : ["contentscript.js"],
-      "run_at" : "document_idle",
-      "all_frames" : false
-    }
-  ],
+  "permissions": [ "declarativeContent" ],
   "icons" : {
-    "48" : "sandwich-48.png",
-    "128" : "sandwich-128.png"
+    "48" : "video-48.png",
+    "128" : "video-128.png"
   },
   "manifest_version": 2
-}
+}