Remove 'Enable' button on unsupported platforms. Added 'No hosts' message.

remoting/webapp/main.css

Index: remoting/webapp/main.css
diff --git a/remoting/webapp/main.css b/remoting/webapp/main.css
index f6cc0cc9198266c249576d9f1b567f58ad581032..7139592ed6a4a5bf246210fd990c3dbc122c81d8 100644
--- a/remoting/webapp/main.css
+++ b/remoting/webapp/main.css
@@ -243,6 +243,7 @@ h2 {
   line-height:24px;
   font-weight: normal;
   color: #222;
+  margin-bottom: 10px;
 }
 
 section > h2 {
@@ -371,11 +372,6 @@ section {
   min-width: 72px;
 }
 
-.host-list-table {
-  width: 100%;
-  border-spacing: 0;
-}
-
 td {
   vertical-align: middle;
 }
@@ -561,7 +557,7 @@ button {
 }
 
 #webapp-description {
-  margin: 10px 0;
+  margin-bottom: 10px;
 }
 
 #why-is-this-safe {