GitLab

- Apply color and line-height to the whole page
- Set iron-icon-width/height globally, reducing the number of places
  where specific sizing is necessary
- Import cr-shared-style into Bookmarks' shared style module, which
  removes the need to specify some button styles
- Use paper-icon-button-light in folder-node, which simplifies CSS and
  slightly improves performance
- Make item highlight colors consistent

BUG=715394
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:closure_compilation

Review-Url: https://codereview.chromium.org/2846673003
Cr-Commit-Position: refs/heads/master@{#468296}