What kind of change does this PR introduce? (check at least one)

• Bugfix
• Feature
• Code style update
• Refactor
• Build-related changes
• Other, please describe:

Does this PR introduce a breaking change? (check one)

• Yes
• No

The PR fulfills these requirements:

• It's submitted to the dev branch for v2.x (or to a previous version branch), not the master branch
• When resolving a specific issue, it's referenced in the PR's title (e.g. fix #xxx[,#xxx], where "xxx" is the issue number)
• All tests are passing: https://github.com/vuejs/vue/blob/dev/.github/CONTRIBUTING.md#development-setup
• New/updated tests are included

Other information:

On IE9, we are currently marking vmodel flag in real DOM and virtually trigger input event when selectionchange is triggered by the element. But input[type=password] element is not set vmodel flag since it does not match the condition.

BTW, should we also add conditions for other input types that can be input texts like search, url and so on?