Update targetSdkVersion for Chromium applications.

Behavior changes described here:
http://developer.android.com/about/versions/android-5.0.html

BUG=424680

TBR=aa@chromium.org

Review URL: https://codereview.chromium.org/664163003

Cr-Commit-Position: refs/heads/master@{#300506}
[chromedriver] Add support for all target types from DevToolsTargetImpl

BUG=chromedriver:916

Review URL: https://codereview.chromium.org/654713004

Cr-Commit-Position: refs/heads/master@{#300522}