ChromeOS Gaia: UI polishing
-Fixed Enterprise Enrollment window size
-Added autocomplete option to the offline login
-Added default domain "gmail.com" on offline login when user do not enter domain
-gaia-core-icon-button does not have box-shadow when it is hovered
BUG=
480449,
479128,
478453,
478452
Committed:
https://crrev.com/2d816075d4793faf9cbd1e396d9818b81f1e91ef
Cr-Commit-Position: refs/heads/master@{#327043}