Why I cannot submit a form in a new tab using extension content script

[sunxcint]

After updating to Chrome 6, the form submission with target attribute
value "_blank" will cause a new simple window pop up rather than a new
tab like in Chrome 5.X. Will you please tell me an alternative
solution in which a tab (not a may-be-blocked simple window) be pop
up when submitting a form.

[Aaron Boodman]

Do you have a small reproducible test case? I probably can't fix it
for Chrome 6, but I've been working in this area for Chrome 7 and
would like to fix it there.

- a

[Tao Sun]

The simple test case is in attachment. The reproducing step:

1. Load the extension.
2. Open any pages in a tab

Then a new simple window will be pop up and navigated(POST) to www.google.com.