content: convert SSL notifications to observer usage

chrome/browser/ssl/ssl_tab_helper.h

Index: chrome/browser/ssl/ssl_tab_helper.h
diff --git a/chrome/browser/ssl/ssl_tab_helper.h b/chrome/browser/ssl/ssl_tab_helper.h
index 590de9c5182ed4d85e2a6d25681bb89b3cf30d98..6acd9fef6ccf824e205c75c374328ec79d7a1f0c 100644
--- a/chrome/browser/ssl/ssl_tab_helper.h
+++ b/chrome/browser/ssl/ssl_tab_helper.h
@@ -10,6 +10,7 @@
 #include "base/callback_forward.h"
 #include "base/memory/linked_ptr.h"
 #include "base/memory/ref_counted.h"
+#include "content/public/browser/web_contents_observer.h"
 #include "content/public/browser/web_contents_user_data.h"
 
 class SSLAddCertHandler;
@@ -20,10 +21,14 @@ class SSLCertRequestInfo;
 class X509Certificate;
 }
 
-class SSLTabHelper : public content::WebContentsUserData<SSLTabHelper> {
+class SSLTabHelper : public content::WebContentsObserver,
+  public content::WebContentsUserData<SSLTabHelper> {
  public:
   virtual ~SSLTabHelper();
 
+  // content::WebContentsObserver:
+  virtual void DidChangeVisibleSSLState() OVERRIDE;
+
   // Called when |handler| encounters an error in verifying a received client
   // certificate. Note that, because CAs often will not send us intermediate
   // certificates, the verification we can do is minimal: we verify the