PasswordManager fills up text input field with password, or PM crashes chrome tab/window/session
PasswordManager fills up text input field with password, or PM crashes chrome tab/window/session

The password manager was incorrectly down-casting from WebNode to WebInputElement and then upon method invocation, was crashing.  This change adds extra checks to |FindFormInputElements| before down-casting.  Also, when "name" attributes are ambiguous, the code now rejects filling.  This fixes the case where password text can erroneously get filled in the username field.

BUG=29352
TEST=PasswordAutocompleteManagerTest.*, and manual according to bugs.

Review URL: http://codereview.chromium.org/6271007

git-svn-id: dd90618784b6a4b323ea0c23a071cb1c9e6f2ac7@71806 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser