Browser: Update UI with new components and elements (#5671)

browser/app/less/inc/base.less

@@ -1,6 +1,9 @@
 * {
     -webkit-font-smoothing: antialiased;
     -moz-osx-font-smoothing: grayscale;
+    box-sizing: border-box;
+    -webkit-box-sizing: border-box;
+    -moz-box-sizing: border-box;
 
     &:focus,
     &:active {
@@ -9,23 +12,35 @@
 }
 
 html {
-    font-size: 10px;
-    -webkit-tap-highlight-color: rgba(0,0,0,0);
-}
-
-html,
-body {
+    font-size: @font-size-base;
     min-height: 100%;
 }
 
-a {
-    .transition(color);
-    .transition-duration(300ms);
+body {
+    background-color: @body-bg;
+    font-weight: @font-weight-normal;
+    font-family: @font-family-sans-serif;
+    line-height: @line-height-base;
+    color: @text-color;
+}
 
+h1, h2, h3, h4, h5, h6 {
+    font-family: @headings-font-family;
+    color: @headings-color;
+    font-weight: @font-weight-bold;
+}
+
+a {
+    color: @link-color;
+    text-decoration: @link-hover-decoration;
+
+    &:hover {
+        color: darken(@link-color, 10%);
+    }
 }
 
 button {
     border: 0;
-}
-
-
+    background-color: transparent;
+    padding: 0;
+}