Views/Harmony: Replace layout constants in chrome/browser/ui/views/extensions.

Replace all direct references to constants in ui/views/layout/layout_constants.h
under chrome/browser/ui/views/extensions/* with LayoutDelegate metrics.

BUG=691897

Review-Url: https://codereview.chromium.org/2753243002
Cr-Commit-Position: refs/heads/master@{#459707}
9 files changed