Always use arc::InstanceHolder<T>::GetInstanceForMethod

chrome/browser/memory/tab_manager_delegate_chromeos.h

Index: chrome/browser/memory/tab_manager_delegate_chromeos.h
diff --git a/chrome/browser/memory/tab_manager_delegate_chromeos.h b/chrome/browser/memory/tab_manager_delegate_chromeos.h
index 0ca4e26c02dad21c8d1c44d2ab63d8a0f77e0f0c..fe3fd10deaea78628af733e2abd6f13580f64af2 100644
--- a/chrome/browser/memory/tab_manager_delegate_chromeos.h
+++ b/chrome/browser/memory/tab_manager_delegate_chromeos.h
@@ -47,11 +47,9 @@ enum class ProcessType {
 
 // The Chrome OS TabManagerDelegate is responsible for keeping the
 // renderers' scores up to date in /proc/<pid>/oom_score_adj.
-class TabManagerDelegate
-    : public arc::InstanceHolder<arc::mojom::ProcessInstance>::Observer,
-      public aura::client::ActivationChangeObserver,
-      public content::NotificationObserver,
-      public chrome::BrowserListObserver {
+class TabManagerDelegate : public aura::client::ActivationChangeObserver,
+                           public content::NotificationObserver,
+                           public chrome::BrowserListObserver {
  public:
   class MemoryStat;
 
@@ -64,10 +62,6 @@ class TabManagerDelegate
 
   void OnBrowserSetLastActive(Browser* browser) override;
 
-  // InstanceHolder<arc::mojom::ProcessInstance>::Observer overrides.
-  void OnInstanceReady() override;
-  void OnInstanceClosed() override;
-
   // aura::ActivationChangeObserver overrides.
   void OnWindowActivated(
       aura::client::ActivationChangeObserver::ActivationReason reason,
@@ -176,11 +170,6 @@ class TabManagerDelegate
   // Util for getting system memory status.
   std::unique_ptr<TabManagerDelegate::MemoryStat> mem_stat_;
 
-  // Holds a weak pointer to arc::mojom::ProcessInstance.
-  arc::mojom::ProcessInstance* arc_process_instance_;
-  // Current ProcessInstance version.
-  int arc_process_instance_version_;
-
   // Reports UMA histograms.
   std::unique_ptr<UmaReporter> uma_;