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

chrome/browser/webdata/keyword_table.h

Index: chrome/browser/webdata/keyword_table.h
===================================================================
--- chrome/browser/webdata/keyword_table.h	(revision 109953)
+++ chrome/browser/webdata/keyword_table.h	(working copy)
@@ -13,13 +13,8 @@
 #include "chrome/browser/webdata/web_database_table.h"
 #include "chrome/browser/search_engines/template_url_id.h"
 
-class GURL;
 class TemplateURL;
 
-namespace base {
-class Time;
-}
-
 // This class manages the |keywords| MetaTable within the SQLite database
 // passed to the constructor. It expects the following schema:
 //