GitLab

This patch:
 1. Adds a camera image icon. Currently just sets a cameraActive
    property and hides the static image preview pane, but functionality
    will expand in subsquent patches.
 2. Adds a preview pane as described in the mocks for the selected
    image.

BUG=563721

Review URL: https://codereview.chromium.org/1610973002

Cr-Commit-Position: refs/heads/master@{#370796}