Use same UI style for popup and plugin blocking UI.

Screenshots:

Old plugin blocking UI: https://drive.google.com/file/d/0B9q2eN9gDoUIX1NFVjAtY0w2V2c/view?usp=sharing
New plugin blocking UI: https://drive.google.com/file/d/0B9q2eN9gDoUITk5jVDVuZDIwUmc/view?usp=sharing
New plugin blocking UI (Mac): https://drive.google.com/file/d/0B9q2eN9gDoUIc3RhLVdzVExOQTQ/view?usp=sharing

Old popup blocking UI: https://drive.google.com/file/d/0B9q2eN9gDoUIZzdTZHg4czJCMFU/view?usp=sharing
New popup blocking UI (unchanged): https://drive.google.com/file/d/0B9q2eN9gDoUIVFFNNXRDU1dDWTQ/view?usp=sharing

BUG=414399

Review URL: https://codereview.chromium.org/1025503002

Cr-Commit-Position: refs/heads/master@{#322295}
8 files changed