Update the visuals of about:flags "Relaunch Now" button.

Make it visually aligned with other buttons from chrome error
pages.  Make it easier to see by giving it more contrast.  Update
the formatting to remove an explicit height being set to give a
nicer look on various orientations of devices.

BUG=486816

Review URL: https://codereview.chromium.org/1136133003

Cr-Commit-Position: refs/heads/master@{#329271}

chrome/browser/resources/flags.css

@@ -7,8 +7,8 @@ body {
 <if expr="not is_android and not is_ios">
   min-width: 47em;
 </if>
-  /* Should match needs-restart.height + 5 */
-  padding-bottom: 75px;
+  /* Should be larger than the evaluated height of needs-restart. */
+  padding-bottom: 100px;
 }
 
 a {
@@ -164,14 +164,14 @@ html[dir=rtl] #experiment-reset-all {
 }
 
 div.needs-restart {
+  /* If you modify properties that change the height of this,
+   * update body.padding-bottom. */
   background: #FFF;
   border-top: 1px solid rgb(181, 199, 222);
   bottom: 0;
   box-sizing: border-box;
-  /* If you change this, update body.padding-bottom */
-  height: 70px;
   left: 0;
-  padding-bottom: 25px;
+  padding-bottom: 15px;
   padding-left: 15px;
   padding-right: 15px;
   padding-top: 15px;
@@ -179,6 +179,22 @@ div.needs-restart {
   width: 100%;
 }
 
+.experiment-restart-button {
+  -webkit-user-select: none;
+  background: rgb(76, 142, 250);
+  border: 0;
+  border-radius: 2px;
+  box-sizing: border-box;
+  color: #fff;
+  cursor: pointer;
+  font-size: .875em;
+  font-weight: 600;
+  margin-top: 10px;
+  padding: 10px 24px;
+  text-transform: uppercase;
+  transition: box-shadow 200ms cubic-bezier(0.4, 0, 0.2, 1);
+}
+
 button {
   font-size: 104%;
 }