Refine font sizes on chrome://reset-password

Minor css style changes to make its style closer to other interstitials.

Bug: 848023
Cq-Include-Trybots: luci.chromium.try:closure_compilation
Change-Id: Ie575267fd6b424dd302fb3caf6db23669a778e92
Reviewed-on: https://chromium-review.googlesource.com/1129635Reviewed-by: Carlos IL <carlosil@chromium.org>
Commit-Queue: Jialiu Lin <jialiul@chromium.org>
Cr-Commit-Position: refs/heads/master@{#573470}

chrome/browser/resources/reset_password/reset_password.html

@@ -15,15 +15,21 @@
   <script src="reset_password.mojom.js"></script>
   <script src="reset_password.js"></script>
   <style>
+    html {
+      font-size: 125%;
+    }
+
     body {
       background-color: white;
       color: var(--google-grey-700);
       font-family: system-ui;
+      font-size: 75%;
       word-wrap: break-word;
     }
 
     p {
-      font-size: 1rem;
+      font-size: 1em;
+      line-height: 1.6em;
     }
 
     button {
@@ -34,7 +40,7 @@
       color: white;
       cursor: pointer;
       float: right;
-      font-size: .875rem;
+      font-size: .875em;
       margin: 0;
       padding: 10px 24px;
       transition: box-shadow 200ms cubic-bezier(0.4, 0, 0.2, 1);
@@ -58,15 +64,15 @@
 
     .heading {
       color: var(--paper-grey-800);
-      font-size: 1.6rem;
+      font-size: 1.6em;
       font-weight: normal;
-      line-height: 1.25rem;
+      line-height: 1.25em;
       margin-bottom: 16px;
     }
 
     .page-wrapper {
       box-sizing: border-box;
-      line-height: 1.6rem;
+      line-height: 1.6em;
       margin: 14vh auto 0;
       max-width: 600px;
     }