chromeos: power: Refactor RendererFreezer and add tests

chrome/browser/chromeos/power/renderer_freezer.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CHROME_BROWSER_CHROMEOS_POWER_RENDERER_FREEZER_H_
 #define CHROME_BROWSER_CHROMEOS_POWER_RENDERER_FREEZER_H_
 
 #include "base/callback.h"
-#include "base/files/file_path.h"
+#include "base/memory/scoped_ptr.h"
 #include "base/memory/weak_ptr.h"
 #include "base/time/time.h"
 #include "chromeos/chromeos_export.h"
 #include "chromeos/dbus/power_manager_client.h"
 
 namespace chromeos {
 
 // Freezes the chrome renderers when the system is about to suspend and thaws
 // them after the system fully resumes.  This class registers itself as a
 // PowerManagerClient::Observer on creation and unregisters itself on
 // destruction.
 class CHROMEOS_EXPORT RendererFreezer : public PowerManagerClient::Observer {
  public:
-  RendererFreezer();
+  class Delegate {
+   public:
+    virtual ~Delegate() {}
+
+    // Freezes the chrome renderers.  Returns true if the operation was
+    // successful.
+    virtual bool FreezeRenderers() = 0;
+
+    // Thaws the chrome renderers.  Returns true if the operation was
+    // successful.
+    virtual bool ThawRenderers() = 0;
+
+    // Returns true iff the delegate is capable of freezing renderers.
+    virtual bool CanFreezeRenderers() = 0;
+  };
+
+  explicit RendererFreezer(scoped_ptr<Delegate> delegate);
   virtual ~RendererFreezer();
 
   // PowerManagerClient::Observer implementation
   virtual void SuspendImminent() OVERRIDE;
   virtual void SuspendDone(const base::TimeDelta& sleep_duration) OVERRIDE;
 
  private:
+  // Called when all asynchronous work is complete and renderers can be frozen.
   void OnReadyToSuspend();
 
-  base::FilePath state_path_;
-  bool enabled_;
   bool frozen_;
 
+  scoped_ptr<Delegate> delegate_;
+
   // Callback used to asynchronously report suspend readiness.
   base::Closure suspend_readiness_callback_;
 
   base::WeakPtrFactory<RendererFreezer> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(RendererFreezer);
 };
 
 }  // namespace chromeos
 
 #endif  // CHROME_BROWSER_CHROMEOS_POWER_RENDERER_FREEZER_H_