[Assistant Opt-in] Adaptive to small screens

Smaller screen treatment for padding and scaling:
https://spec.googleplex.com/crosux-spec/feature-specs/oobe-system-window.html

Bug: 1033273
Test: Manual Test
Change-Id: I9938b1c728d66f1a914138102fe3ea466b08875c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2079544Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Commit-Queue: Yue Li <updowndota@chromium.org>
Cr-Commit-Position: refs/heads/master@{#745570}

chrome/browser/resources/chromeos/assistant_optin/assistant_get_more.css

@@ -3,7 +3,7 @@
  * found in the LICENSE file. */
 
 #intro-text {
-  padding-bottom: 58px;
+  padding-bottom: 48px;
 }
 
 #ready-img {
@@ -26,3 +26,23 @@
 #toggles-container {
   width: 50%;
 }
+
+@media screen and (max-height: 736px) {
+  #intro-text {
+    padding-bottom: 24px;
+  }
+}
+
+@media screen and (max-height: 536px) {
+  #intro-text {
+    padding-bottom: 16px;
+  }
+
+  #ready-img {
+    height: 160px;
+  }
+
+  .vertical-line {
+    height: 160px;
+  }
+}

chrome/browser/resources/chromeos/assistant_optin/assistant_voice_match.css

@@ -50,6 +50,16 @@
   width: 360px;
 }
 
+@media screen and (max-height: 736px) {
+  #voice-match-animation {
+    height: 150px;
+  }
+
+  #already-setup-animation {
+    height: 240px;
+  }
+}
+
 #intro-container,
 #recording-container,
 #already-setup-container {