Chrome Version       : 53.0.2785.116
OS Version: Linux 4.6.0-1-amd64 #1 SMP Debian 4.6.4-1 (2016-07-18) x86_64 GNU/Linux
URLs (if applicable) :
Other browsers tested:
  Add OK or FAIL after other browsers where you have tested this issue:
     Safari 5: Not testet
  Firefox 4.x: Not testet
     IE 7/8/9: Note test

What steps will reproduce the problem?
1. Create a simple extension that uses declarativeContent to inject any version of jQuery, as the only content script, into any page you like.
2. Reload that page a few times, and at some point you should see an uncaught exception.  It is usually faster to get the exception on a 'fat' page like facebook or twitter, google.com seems to load fast enough that it works 90% of the times.

What is the expected result?
No unhandled exception. The jQuery library should load flawlessly.


What happens instead of that?
On some occasions, it spits out an unhandled exception.  The exception is due to the fact that there is no document.documentElement at the point in time that the script is executed.


Please provide any additional information below. Attach a screenshot if
possible.

I have debugged this quite a lot, and it can be simplified to a simple content script (instead of the jQuery library) that just does:

    console.log("document: " + document + " documentElement: " + document.documentElement);

With the extension loaded, refresh the page a few times until the output shows that document.documentElement is null (see the two attached images, never mind the name of "delay.js", in the image both delay.js and jquery-2.2.4.js is loaded which also shows the error from jQuery).

As far as i can see from this, then the content script is 

This seems to be a race condition, that sometimes executes the script before the page is is being "created", and thus the document.documentElement is still null.  In the jQuery case, this is quite bad, as jQuery expects to be executed in an environment where document.documentElement exists.

I would as minimum have expected the RequestContentScript to be injected at a place in time that was equivalent to `run_at: document_start` for the content_scripts field in the manifest.json file (or the runAt field in the details argument to chrome.tabs.executeScript)

> In the case of "document_start", the files are injected after any files from css, but before any other DOM is constructed or any other script is run. 

So document.documentElement should be set, as at least some of the DOM is created.



Ideally one could specify the same as run_at, as an argument to declarativeContent.RequestContentScript.



I know that the API docs says that RequestContentScript is not in stable, and I have seen from other bug reports that you guys have chosen to let RequestContentScript stay in stable and still keep the warning on the API page, such that you may change the API if neede at some point.
Just so you don't shoot this down, because I'm testing this in stable.


Again I want to stress that testing this on google.com, is usually not that fruitful.  I was just lucky that it failed quite fast on my attached photos.  twitter.com is usually a great page to test against (or just any other page with lots of content, like a newspaper).


My MWE extension consists of the following three files:

manifest.json:

{
  "manifest_version": 2,
  "name": "MWE",
  "version": "0.1",

  "background": {
    "persistent": false,
    "scripts": [
      "eventPage.js"
    ]
  },

  "permissions": [
    "declarativeContent",
    "<all_urls>"
  ]
}


script.js:

console.log("document: " + document + " documentElement: " + document.documentElement + " URL: " + document.URL);


eventPage.js:

var show_page_action = {
    conditions: [
        new chrome.declarativeContent.PageStateMatcher({
            pageUrl: {
                urlMatches: '.*',
                //schemes: ['https'],
            }
        })
    ],
    actions: [
        new chrome.declarativeContent.RequestContentScript({
            js: ["script.js",
                 //"jquery-2.2.4.js",
                ],
        })
    ],
};

// Make sure our declarativeContent rules are up to date.
chrome.runtime.onInstalled.addListener(function (details) {
    chrome.declarativeContent.onPageChanged.removeRules(undefined, function() {
        chrome.declarativeContent.onPageChanged.addRules([show_page_action])
    })
});





UserAgentString: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/53.0.2785.116 Safari/537.36
 

Deleted: documentElement is HTMLHtmlElement.png 35.5 KB

	documentElement is HTMLHtmlElement.png 35.5 KB View Download

Deleted: documentElement is null.png 45.6 KB

	documentElement is null.png 45.6 KB View Download