Chrome OS OOBE: Make dialog icons match button colors.

Bug: 852551
Change-Id: Ie7b3a95dee5ed135661f47f765e0fb37adb84273
Reviewed-on: https://chromium-review.googlesource.com/1171958Reviewed-by: Wenzhao (Colin) Zang <wzang@chromium.org>
Commit-Queue: Alexander Alekseev <alemate@chromium.org>
Cr-Commit-Position: refs/heads/master@{#582474}

chrome/browser/resources/chromeos/login/oobe_dialog.css

@@ -85,5 +85,5 @@
 #oobe-icon-div ::slotted(iron-icon) {
   --iron-icon-height: 32px;
   --iron-icon-width: 32px;
-  --iron-icon-fill-color: var(--google-blue-500);
+  --iron-icon-fill-color: var(--google-blue-600);
 }