[TabManager] Move remaining discard logic from TabStripModel to TabManager.

chrome/browser/memory/tab_manager_web_contents_data.h

 // Copyright 2015 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_MEMORY_TAB_MANAGER_WEB_CONTENTS_DATA_H_
 #define CHROME_BROWSER_MEMORY_TAB_MANAGER_WEB_CONTENTS_DATA_H_
 
-#include "base/supports_user_data.h"
+#include "base/macros.h"
 #include "base/time/time.h"
 #include "chrome/browser/memory/tab_manager.h"
+#include "content/public/browser/web_contents_observer.h"
+#include "content/public/browser/web_contents_user_data.h"
 
 namespace content {
 class WebContents;
 }
 
 namespace memory {
 
-// Manages the information about the discarding state of a tab. This data is
-// stored in WebContents.
-class TabManager::WebContentsData : public base::SupportsUserData::Data {
+// Internal class used by TabManager to record the needed data for
+// WebContentses.
+class TabManager::WebContentsData
+    : public content::WebContentsObserver,
+      public content::WebContentsUserData<TabManager::WebContentsData> {
  public:
-  // Returns the WebContentsData associated with |web_contents|. It will create
-  // one if none exists.
-  static WebContentsData* Get(content::WebContents* web_contents);
+  explicit WebContentsData(content::WebContents* web_contents);
+  ~WebContentsData() override;
 
-  // Sets the WebContentsData of a |web_contents|. The object referenced by
-  // |state| is now owned by |web_contents|
-  static void Set(content::WebContents* web_contents, WebContentsData* state);
+  // WebContentsObserver implementation:
+  void DidStartLoading() override;
+
+  // Returns true if |web_contents| has been discarded to save memory.
+  bool IsDiscarded();
+
+  // Sets/clears the discard state of |web_contents|.
+  void SetDiscardState(bool state);
+
+  // Returns the number of times |web_contents| has been discarded.
+  int DiscardCount();
+
+  // Increments the number of times |web_contents| has been discarded.
+  void IncrementDiscardCount();
+
+  // Returns true if audio has recently been audible from the WebContents.
+  bool IsRecentlyAudible();
+
+  // Set/clears the state of whether audio has recently been audible from the
+  // WebContents.
+  void SetRecentlyAudible(bool state);
+
+  // Returns the timestamp of the last time |web_contents| changed its audio
+  // state.
+  base::TimeTicks LastAudioChangeTime();
+
+  // Sets the timestamp of the last time |web_contents| changed its audio state.
+  void SetLastAudioChangeTime(base::TimeTicks timestamp);
 
   // Copies the discard state from |old_contents| to |new_contents|.
   static void CopyState(content::WebContents* old_contents,
                         content::WebContents* new_contents);
 
-  // Returns true if |web_contents| has been discarded to save memory.
-  static bool IsDiscarded(content::WebContents* web_contents);
+ private:
+  struct Data {
+    Data();
+    // Is the tab currently discarded?
+    bool is_discarded_;
+    // Number of times the tab has been discarded.
+    int discard_count_;
+    // Is the tab playing audio?
+    bool is_recently_audible_;
+    // Last time the tab started or stopped playing audio (we record the
+    // transition time).
+    base::TimeTicks last_audio_change_time_;
+    // The last time the tab was discarded.
+    base::TimeTicks last_discard_time_;
+  };
 
-  // Sets/clears the discard state of |web_contents|.
-  static void SetDiscardState(content::WebContents* web_contents, bool state);
+  Data tab_data_;
 
-  // Returns the number of times |web_contents| has been discarded.
-  static int DiscardCount(content::WebContents* web_contents);
-
-  // Increments the number of times |web_contents| has been discarded.
-  static void IncrementDiscardCount(content::WebContents* web_contents);
-
-  // Returns true if audio has recently been audible from the WebContents.
-  static bool IsRecentlyAudible(content::WebContents* web_contents);
-
-  // Set/clears the state of whether audio has recently been audible from the
-  // WebContents.
-  static void SetRecentlyAudible(content::WebContents* web_contents,
-                                 bool state);
-
-  // Returns the timestamp of the last time |web_contents| changed its audio
-  // state.
-  static base::TimeTicks LastAudioChangeTime(
-      content::WebContents* web_contents);
-
-  // Sets the timestamp of the last time |web_contents| changed its audio state.
-  static void SetLastAudioChangeTime(content::WebContents* web_contents,
-                                     base::TimeTicks timestamp);
-
- private:
-  WebContentsData();
-
-  // Is the tab currently discarded?
-  bool is_discarded_;
-
-  // Number of times the tab has been discarded.
-  int discard_count_;
-
-  // Is the tab playing audio?
-  bool is_recently_audible_;
-
-  // Last time the tab started or stopped playing audio (we record the
-  // transition time).
-  base::TimeTicks last_audio_change_time_;
-
-  // The last time the tab was discarded.
-  base::TimeTicks last_discard_time_;
+  DISALLOW_COPY_AND_ASSIGN(WebContentsData);
 };
 
 }  // namespace memory
 
 #endif  // CHROME_BROWSER_MEMORY_TAB_MANAGER_WEB_CONTENTS_DATA_H_