The official way to disable the popup is this:

1. Pack your extension: go to chrome://extensions, check Developer mode and click Pack extension

2. Install the extension by dragging and dropping the .crx file into the chrome://extensions page.

You'll get an "Unsupported extensions disabled" popup if you try restarting Chrome at this point.

Then for Windows 7 or Windows 8:

3. Download Chrome group policy templates here
4. Copy [zip]\windows\admx\chrome.admx to c:\windows\policydefinitions
5. Copy [zip]\windows\admx\[yourlanguage]\chrome.adml to c:\windows\policydefinitions\[yourlanguage]\chrome.adml (not c:\windows\[yourlanguage])
6. In Chrome, go to the Extensions page: chrome://extensions
7. Check Developer Mode
8. Scroll down the list of disabled extensions and note the ID(s) of the extensions you want to enable.
9. Click Start > Run, type gpedit.msc and hit enter.
10. Click User Configuration > Administrative Templates > Google Chrome > Extensions
11. Double click Configure extension installation whitelist policy
12. Select Enabled, and click Show
13. In the list, enter the ID(s) of the extensions you noted in Step 7
14. Click OK and restart Chrome.

That's it!

EDIT: As of July 2018, this approach no longer works: it seems Google has stopped honouring the "whitelist".

EDIT 2: As of December 2018, this approach works in Chrome Version 69.0.3497.100 (Official Build) (64-bit):

1. Temporarily enable Developer mode in chrome://extensions

2. Uninstall the extension that causes the popup using the Load unpacked.

3. Click on Pack extension, and find and select the folder containing the extension files. Don't enter the private key file if you don't have it.

4. Click Pack extension. A .crx and .pem file will be created near the root directory of the extension. Install the extension using the .crx file and keep the .pem file safe.

5. Copy the .crx installed extension ID to the whitelist and restart Chrome.

The popup should be gone.

While creating chrome driver, use option to disable it. Its working without any extensions.

Use following code snippet

ChromeOptions options = new ChromeOptions();options.addArguments("chrome.switches","--disable-extensions");System.setProperty("webdriver.chrome.driver",(System.getProperty("user.dir") + "//src//test//resources//chromedriver_new.exe"));driver = new ChromeDriver(options);

As of May 2015 Chrome beta/dev/canary on Windows (see lines 75-78) always display this warning.

• I've just patched chrome.dll (dev channel, 32-bit) using hiew32 demo version: run it, switch to hex view (Enter key), search for ExtensionDeveloperModeWarning (F7) then press F6 to find the referring code, go to nearby INC EAX line, which is followed by RETN, press F3 to edit, type 90 instead of 40, which will be rendered as NOP (no-op), save (F9).

• Simplified method found by @Gsx, which also works for 64-bit Chrome dev:

  1. run hiew32 demo (in admin mode) and open Chrome.dll
  2. switch to hex view (Enter key)
  3. search for ExtensionDeveloperModeWarning (F7)
  4. press F3 to edit and replace the first letter "E" with any other character
  5. save (F9).

• patch.BAT script

Of course this will last only until the next update so whoever needs it frequently might write an auto-patcher or a launcher that patches the dll in memory.