Move ActiveStateManagerImpl::Observer to ActiveStateManager.

The observer is thus exposed in ios/web/public and can notably be used
in various components.
Observing the active state allows classes that create and manipulate
WKWebViews to stop and release them when the browser state becomes
inactive and to resume their operation when it becomes active again.

BUG=

Review URL: https://codereview.chromium.org/1310193002

Cr-Commit-Position: refs/heads/master@{#345091}

ios/web/active_state_manager_impl.h

@@ -25,23 +25,8 @@ class ActiveStateManagerImpl : public ActiveStateManager,
   // ActiveStateManager methods.
   void SetActive(bool active) override;
   bool IsActive() override;
-
-  // Observer that is notified when a ActiveStateManager becomes active,
-  // inactive or destroyed.
-  class Observer {
-   public:
-    // Called when the ActiveStateManager becomes active.
-    virtual void OnActive() = 0;
-    // Called when the ActiveStateManager becomes inactive.
-    virtual void OnInactive() = 0;
-    // Called just before the ActiveStateManager is destroyed.
-    virtual void WillBeDestroyed() = 0;
-  };
-  // Adds an observer for this class. An observer should not be added more
-  // than once. The caller retains the ownership of the observer object.
-  void AddObserver(Observer* obs);
-  // Removes an observer.
-  void RemoveObserver(Observer* obs);
+  void AddObserver(ActiveStateManager::Observer* observer) override;
+  void RemoveObserver(ActiveStateManager::Observer* observer) override;
 
  private:
   BrowserState* browser_state_;  // weak, owns this object.

ios/web/active_state_manager_impl.mm

@@ -53,12 +53,12 @@
   return active_;
 }
 
-void ActiveStateManagerImpl::AddObserver(Observer* obs) {
+void ActiveStateManagerImpl::AddObserver(ActiveStateManager::Observer* obs) {
   DCHECK_CURRENTLY_ON_WEB_THREAD(WebThread::UI);
   observer_list_.AddObserver(obs);
 }
 
-void ActiveStateManagerImpl::RemoveObserver(Observer* obs) {
+void ActiveStateManagerImpl::RemoveObserver(ActiveStateManager::Observer* obs) {
   DCHECK_CURRENTLY_ON_WEB_THREAD(WebThread::UI);
   observer_list_.RemoveObserver(obs);
 }

ios/web/active_state_manager_impl_unittest.mm

@@ -20,13 +20,13 @@
 // A test fixture to test ActiveStateManagerImpl.
 typedef WebTest ActiveStateManagerImplTest;
 
-// An ActiveStateManagerImpl::Observer used for testing purposes.
-class ActiveStateManagerImplObserver : public ActiveStateManagerImpl::Observer {
+// An ActiveStateManager::Observer used for testing purposes.
+class ActiveStateManagerObserver : public ActiveStateManager::Observer {
  public:
-  ActiveStateManagerImplObserver() {}
-  virtual ~ActiveStateManagerImplObserver() {}
+  ActiveStateManagerObserver() {}
+  virtual ~ActiveStateManagerObserver() {}
 
-  // ActiveStateManagerImpl::Observer implementation.
+  // ActiveStateManager::Observer implementation.
   MOCK_METHOD0(OnActive, void());
   MOCK_METHOD0(OnInactive, void());
   MOCK_METHOD0(WillBeDestroyed, void());
@@ -55,17 +55,15 @@
   EXPECT_FALSE(active_state_manager->IsActive());
 }
 
-// Tests that ActiveStateManagerImpl::Observer are notified correctly.
+// Tests that ActiveStateManager::Observer are notified correctly.
 TEST_F(ActiveStateManagerImplTest, ObserverMethod) {
   // |GetBrowserState()| already has its ActiveStateManager be active.
   BrowserState::GetActiveStateManager(GetBrowserState())->SetActive(false);
 
-  ActiveStateManagerImplObserver observer;
+  ActiveStateManagerObserver observer;
   TestBrowserState browser_state;
-  ActiveStateManagerImpl* active_state_manager =
-      static_cast<ActiveStateManagerImpl*>(
-          BrowserState::GetActiveStateManager(&browser_state));
-
+  ActiveStateManager* active_state_manager =
+      BrowserState::GetActiveStateManager(&browser_state);
 
   active_state_manager->AddObserver(&observer);
 

ios/web/browsing_data_partition_impl.h

@@ -8,30 +8,29 @@
 #import "base/mac/scoped_nsobject.h"
 #include "base/macros.h"
 #include "base/supports_user_data.h"
-#include "ios/web/active_state_manager_impl.h"
+#include "ios/web/public/active_state_manager.h"
 #include "ios/web/public/browsing_data_partition.h"
 
 @class CRWBrowsingDataStore;
 
 namespace web {
 
-class ActiveStateManagerImpl;
 class BrowserState;
 
 // Concrete subclass of web::BrowsingDataPartition. Observes
-// ActiveStateManagerImpl::Observer methods to trigger stash/restore operations
+// ActiveStateManager::Observer methods to trigger stash/restore operations
 // on the underlying CRWBrowsingDataStore.
 class BrowsingDataPartitionImpl : public BrowsingDataPartition,
                                   public base::SupportsUserData::Data,
-                                  public web::ActiveStateManagerImpl::Observer {
+                                  public web::ActiveStateManager::Observer {
  public:
   explicit BrowsingDataPartitionImpl(BrowserState* browser_state);
   ~BrowsingDataPartitionImpl() override;
 
   // BrowsingDataPartition implementation.
   CRWBrowsingDataStore* GetBrowsingDataStore() override;
 
-  // ActiveStateManagerImpl::Observer implementation.
+  // ActiveStateManager::Observer implementation.
   void OnActive() override;
   void OnInactive() override;
   void WillBeDestroyed() override;
@@ -41,7 +40,7 @@ class BrowsingDataPartitionImpl : public BrowsingDataPartition,
   // The browsing data store backing this object.
   base::scoped_nsobject<CRWBrowsingDataStore> browsing_data_store_;
   // Weak pointer to the associated active state manager.
-  ActiveStateManagerImpl* active_state_manager_;
+  ActiveStateManager* active_state_manager_;
 
   DISALLOW_COPY_AND_ASSIGN(BrowsingDataPartitionImpl);
 };

ios/web/browsing_data_partition_impl.mm

@@ -109,8 +109,7 @@ - (void)observeValueForKeyPath:(NSString*)keyPath
   DCHECK_CURRENTLY_ON_WEB_THREAD(WebThread::UI);
   DCHECK(browser_state);
 
-  active_state_manager_ = static_cast<ActiveStateManagerImpl*>(
-      BrowserState::GetActiveStateManager(browser_state));
+  active_state_manager_ = BrowserState::GetActiveStateManager(browser_state);
   DCHECK(active_state_manager_);
   active_state_manager_->AddObserver(this);
 }

ios/web/public/active_state_manager.h

@@ -23,6 +23,23 @@ class ActiveStateManager {
   // Returns true if the BrowserState is active.
   virtual bool IsActive() = 0;
 
+  // Observer that is notified when a ActiveStateManager becomes active,
+  // inactive or destroyed.
+  class Observer {
+   public:
+    // Called when the ActiveStateManager becomes active.
+    virtual void OnActive() {}
+    // Called when the ActiveStateManager becomes inactive.
+    virtual void OnInactive() {}
+    // Called just before the ActiveStateManager is destroyed.
+    virtual void WillBeDestroyed() {}
+  };
+  // Adds an observer for this class. An observer should not be added more
+  // than once. The caller retains the ownership of the observer object.
+  virtual void AddObserver(Observer* observer) = 0;
+  // Removes an observer.
+  virtual void RemoveObserver(Observer* observer) = 0;
+
  protected:
   virtual ~ActiveStateManager(){};
 };