oobe: simplify css for new dialog

Bug: 1151292
Change-Id: I385d767ae4aee2160f85904afa5bac1da1c7923a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2593607Reviewed-by: Roman Sorokin [CET] <rsorokin@chromium.org>
Commit-Queue: Roman Aleksandrov <raleksandrov@google.com>
Cr-Commit-Position: refs/heads/master@{#837123}

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

@@ -103,7 +103,7 @@ html[new-layout] #oobe {
   padding-top: unset;
 }
 
-#outer-container.fullscreen,
+html:not([new-layout]) #outer-container.fullscreen,
 #outer-container.fullscreen #oobe,
 #inner-container,
 #inner-container > .step {

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

@@ -9,13 +9,13 @@
       rgba(66, 133, 244, 0.4); /* #4284f4 */
 }
 
-.step {
+html:not([new-layout]) .step {
   box-sizing: border-box;
   position: absolute;
   user-select: none;
 }
 
-.new-step {
+html[new-layout] .step {
   box-sizing: border-box;
   height: var(--oobe-adaptive-dialog-height);
   user-select: none;