Refactor Permissions related method out of ContentBrowserClient.

This is creating a content/public/browser/permission_manager.h interface
that is hooked on the BrowserContext. It has an implementation in chrome/
android_webview/, content/shell/ and one for layout tests.

BUG=437770, 430238

Review URL: https://codereview.chromium.org/1011953003

Cr-Commit-Position: refs/heads/master@{#322721}
53 files changed