Do not trigger primary color changes on non-supported toolbar states.

This fixes an issue where you switch from the NTP to a normal tab
where it attempts to transition from transparent to gray on the
toolbar and results in a delayed update to the layout.

BUG=493082

Review URL: https://codereview.chromium.org/1155053003

Cr-Commit-Position: refs/heads/master@{#332240}