Clean up TCW, make it solely a hub for 1:1 observer/helper objects.

chrome/browser/sessions/session_service.cc

Index: chrome/browser/sessions/session_service.cc
diff --git a/chrome/browser/sessions/session_service.cc b/chrome/browser/sessions/session_service.cc
index 0dda61c1c432dd03f77f5ddc05a0e049c8fcf471..546adcc2283e8e45a8ebd8eda71c0429dc96daca 100644
--- a/chrome/browser/sessions/session_service.cc
+++ b/chrome/browser/sessions/session_service.cc
@@ -589,7 +589,7 @@ void SessionService::Observe(int type,
         TabNavigationPathPrunedFromBack(
             tab->restore_tab_helper()->window_id(),
             tab->restore_tab_helper()->session_id(),
-            tab->controller().entry_count());
+            tab->tab_contents()->controller().entry_count());
       }
       RecordSessionUpdateHistogramData(content::NOTIFICATION_NAV_LIST_PRUNED,
           &last_updated_nav_list_pruned_time_);
@@ -618,7 +618,8 @@ void SessionService::Observe(int type,
                   source).ptr()->tab_contents());
       if (!tab || tab->profile() != profile())
         return;
-      int current_entry_index = tab->controller().GetCurrentEntryIndex();
+      int current_entry_index =
+          tab->tab_contents()->controller().GetCurrentEntryIndex();
       SetSelectedNavigationIndex(tab->restore_tab_helper()->window_id(),
                                  tab->restore_tab_helper()->session_id(),
                                  current_entry_index);
@@ -626,7 +627,8 @@ void SessionService::Observe(int type,
           tab->restore_tab_helper()->window_id(),
           tab->restore_tab_helper()->session_id(),
           current_entry_index,
-          *tab->controller().GetEntryAtIndex(current_entry_index));
+          *tab->tab_contents()->controller().GetEntryAtIndex(
+              current_entry_index));
       content::Details<content::LoadCommittedDetails> changed(details);
       if (changed->type == content::NAVIGATION_TYPE_NEW_PAGE ||
         changed->type == content::NAVIGATION_TYPE_EXISTING_PAGE) {
@@ -1140,12 +1142,15 @@ void SessionService::BuildCommandsForTab(
   DCHECK(tab && commands && window_id.id());
   const SessionID& session_id(tab->restore_tab_helper()->session_id());
   commands->push_back(CreateSetTabWindowCommand(window_id, session_id));
-  const int current_index = tab->controller().GetCurrentEntryIndex();
+  const int current_index =
+      tab->tab_contents()->controller().GetCurrentEntryIndex();
   const int min_index = std::max(0,
                                  current_index - max_persist_navigation_count);
-  const int max_index = std::min(current_index + max_persist_navigation_count,
-                                 tab->controller().entry_count());
-  const int pending_index = tab->controller().pending_entry_index();
+  const int max_index =
+      std::min(current_index + max_persist_navigation_count,
+               tab->tab_contents()->controller().entry_count());
+  const int pending_index =
+      tab->tab_contents()->controller().pending_entry_index();
   if (tab_to_available_range) {
     (*tab_to_available_range)[session_id.id()] =
         std::pair<int, int>(min_index, max_index);
@@ -1163,8 +1168,8 @@ void SessionService::BuildCommandsForTab(
   }
   for (int i = min_index; i < max_index; ++i) {
     const NavigationEntry* entry = (i == pending_index) ?
-        tab->controller().pending_entry() :
-        tab->controller().GetEntryAtIndex(i);
+        tab->tab_contents()->controller().pending_entry() :
+        tab->tab_contents()->controller().GetEntryAtIndex(i);
     DCHECK(entry);
     if (ShouldTrackEntry(entry->virtual_url())) {
       commands->push_back(