Cleanup: Remove unneeded forward declarations from various chrome/browser subdirectories.

chrome/browser/safe_browsing/malware_details_history.h

Index: chrome/browser/safe_browsing/malware_details_history.h
===================================================================
--- chrome/browser/safe_browsing/malware_details_history.h	(revision 109953)
+++ chrome/browser/safe_browsing/malware_details_history.h	(working copy)
@@ -21,8 +21,6 @@
 #include "content/public/browser/notification_registrar.h"
 #include "net/base/completion_callback.h"
 
-class TabContents;
-
 namespace safe_browsing {
 typedef std::vector<GURL> RedirectChain;
 }
@@ -32,7 +30,6 @@
           MalwareDetailsRedirectsCollector,
           content::BrowserThread::DeleteOnUIThread>,
       public content::NotificationObserver {
-
  public:
   explicit MalwareDetailsRedirectsCollector(Profile* profile);
   virtual ~MalwareDetailsRedirectsCollector();