Reland of Moving previews code from components/ to chrome/

components/previews/core/previews_io_data.h

Index: components/previews/core/previews_io_data.h
diff --git a/components/previews/core/previews_io_data.h b/components/previews/core/previews_io_data.h
index a30ab6ff0764bcf6ce4ce0f443918ca1e6429f42..f6e85331562eaf47f76ed321e31020e3682036ea 100644
--- a/components/previews/core/previews_io_data.h
+++ b/components/previews/core/previews_io_data.h
@@ -8,6 +8,7 @@
 #include <memory>
 #include <string>
 
+#include "base/callback.h"
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/weak_ptr.h"
@@ -27,6 +28,8 @@ class PreviewsBlackList;
 class PreviewsOptOutStore;
 class PreviewsUIService;
 
+typedef base::Callback<bool(PreviewsType)> PreviewsIsEnabledCallback;
+
 // A class to manage the IO portion of inter-thread communication between
 // previews/ objects. Created on the UI thread, but used only on the IO thread
 // after initialization.
@@ -40,7 +43,8 @@ class PreviewsIOData : public PreviewsDecider {
   // Stores |previews_ui_service| as |previews_ui_service_| and posts a task to
   // InitializeOnIOThread on the IO thread.
   void Initialize(base::WeakPtr<PreviewsUIService> previews_ui_service,
-                  std::unique_ptr<PreviewsOptOutStore> previews_opt_out_store);
+                  std::unique_ptr<PreviewsOptOutStore> previews_opt_out_store,
+                  const PreviewsIsEnabledCallback& is_enabled_callback);
 
   // Adds a navigation to |url| to the black list with result |opt_out|.
   void AddPreviewNavigation(const GURL& url, bool opt_out, PreviewsType type);
@@ -75,6 +79,9 @@ class PreviewsIOData : public PreviewsDecider {
   scoped_refptr<base::SingleThreadTaskRunner> ui_task_runner_;
   scoped_refptr<base::SingleThreadTaskRunner> io_task_runner_;
 
+  // Whether the preview is enabled. Valid after Initialize() is called.
+  PreviewsIsEnabledCallback is_enabled_callback_;
+
   base::WeakPtrFactory<PreviewsIOData> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(PreviewsIOData);