Upstream Chrome on iOS source code [2/11].

ios/chrome/browser/metrics/tab_usage_recorder.h

Index: ios/chrome/browser/metrics/tab_usage_recorder.h
diff --git a/ios/chrome/browser/metrics/tab_usage_recorder.h b/ios/chrome/browser/metrics/tab_usage_recorder.h
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+// Copyright 2013 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 IOS_CHROME_BROWSER_METRICS_TAB_USAGE_RECORDER_H_
+#define IOS_CHROME_BROWSER_METRICS_TAB_USAGE_RECORDER_H_
+
+#import <Foundation/Foundation.h>
+#include <deque>
+#include <map>
+
+#include "base/ios/weak_nsobject.h"
+#include "base/macros.h"
+#include "base/time/time.h"
+#import "ios/chrome/browser/metrics/tab_usage_recorder_delegate.h"
+
+@class Tab;
+
+// Histogram names (visible for testing only).
+
+// The prefix of the histogram names.  Used to create a HistogramRecorder.
+extern const char kTabUsageHistogramPrefix[];
+
+// The name of the histogram that records the state of the selected tab
+// (i.e. the tab being switched to).
+extern const char kSelectedTabHistogramName[];
+
+// The name of the histogram that records the number of page loads before an
+// evicted tab is selected.
+extern const char kPageLoadsBeforeEvictedTabSelected[];
+
+// The name of the histogram tracking the reload time for a previously-evicted
+// tab.
+extern const char kEvictedTabReloadTime[];
+
+// The name of the histogram for whether or not the reload of a
+// previously-evicted tab completed successfully.
+extern const char kEvictedTabReloadSuccessRate[];
+
+// The name of the histogram for whether or not the user switched tabs before an
+// evicted tab completed reloading.
+extern const char kDidUserWaitForEvictedTabReload[];
+
+// The name of the histogram that records time intervals between restores of
+// previously-evicted tabs.  The first restore seen in a session will record the
+// time since the session started.
+extern const char kTimeBetweenRestores[];
+
+// The name of the histogram that records time intervals between the last
+// restore of a previously-evicted tab and the end of the session.
+extern const char kTimeAfterLastRestore[];
+
+// Name of histogram to record whether a memory warning had been recently
+// received when a renderer termination occurred.
+extern const char kRendererTerminationSawMemoryWarning[];
+
+// Name of histogram to record the number of alive renderers when a renderer
+// termination is received.
+extern const char kRendererTerminationAliveRenderers[];
+
+// Name of histogram to record the number of renderers that were alive shortly
+// before a renderer termination. This metric is being recorded in case the OS
+// kills renderers in batches.
+extern const char kRendererTerminationRecentlyAliveRenderers[];
+
+// The recently alive renderer count metric counts all renderers that were alive
+// x seconds before a renderer termination. |kSecondsBeforeRendererTermination|
+// specifies x.
+extern const int kSecondsBeforeRendererTermination;
+
+// Reports usage about the lifecycle of a single TabModel's tabs.
+class TabUsageRecorder {
+ public:
+  enum TabStateWhenSelected {
+    IN_MEMORY = 0,
+    EVICTED,
+    EVICTED_DUE_TO_COLD_START,
+    PARTIALLY_EVICTED,             // Currently, used only by Android.
+    EVICTED_DUE_TO_BACKGROUNDING,  // Deprecated
+    EVICTED_DUE_TO_INCOGNITO,
+    RELOADED_DUE_TO_COLD_START_FG_TAB_ON_START,   // Android.
+    RELOADED_DUE_TO_COLD_START_BG_TAB_ON_SWITCH,  // Android.
+    LAZY_LOAD_FOR_OPEN_IN_NEW_TAB,                // Android
+    STOPPED_DUE_TO_LOADING_WHEN_BACKGROUNDING,    // Deprecated.
+    EVICTED_DUE_TO_LOADING_WHEN_BACKGROUNDING,    // Deprecated.
+    EVICTED_DUE_TO_RENDERER_TERMINATION,
+    TAB_STATE_COUNT,
+  };
+
+  enum LoadDoneState {
+    LOAD_FAILURE,
+    LOAD_SUCCESS,
+    LOAD_DONE_STATE_COUNT,
+  };
+
+  enum EvictedTabUserBehavior {
+    USER_WAITED,
+    USER_DID_NOT_WAIT,
+    USER_LEFT_CHROME,
+    USER_BEHAVIOR_COUNT,
+  };
+
+  // |delegate| is the TabUsageRecorderDelegate which provides access to the
+  // Tabs which this TabUsageRecorder is monitoring. |delegate| can be nil.
+  explicit TabUsageRecorder(id<TabUsageRecorderDelegate> delegate);
+  virtual ~TabUsageRecorder();
+
+  // Called during startup when the tab model is created, or shortly after a
+  // post-crash launch if the tabs are restored.  |tabs| is an array containing
+  // the tabs being restored in the current tab model. |active_tab| is the tab
+  // currently in the foreground.
+  void InitialRestoredTabs(Tab* active_tab, NSArray* tabs);
+
+  // Called when a tab is created for immediate selection.
+  void TabCreatedForSelection(Tab* tab);
+
+  // Called when a tab switch is made.  Determines what value to record, and
+  // when to reset the page load counter.
+  void RecordTabSwitched(Tab* old_tab, Tab* new_tab);
+
+  // Called when the tab model which the user is primarily interacting with has
+  // changed. The |active_tab| is the current tab of the tab model. If the user
+  // began interacting with |active_tab|, |primary| should be true. If the user
+  // stopped interacting with |active_tab|, |primary| should be false.
+  void RecordPrimaryTabModelChange(BOOL primary, Tab* active_tab);
+
+  // Called when a page load begins, to keep track of how many page loads
+  // happen before an evicted tab is seen.
+  void RecordPageLoadStart(Tab* tab);
+
+  // Called when a page load finishes, to track the load time for evicted tabs.
+  void RecordPageLoadDone(Tab* tab, bool success);
+
+  // Called when there is a user-initiated reload.
+  void RecordReload(Tab* tab);
+
+  // Called when WKWebView's renderer is terminated. |tab| contains the tab
+  // whose renderer was terminated, and |visible| indicates whether or not the
+  // tab was visible when the renderer terminated.
+  void RendererTerminated(Tab* tab, bool visible);
+
+  // Called when the app has been backgrounded.
+  void AppDidEnterBackground();
+
+  // Called when the app has been foregrounded.
+  void AppWillEnterForeground();
+
+  // Resets the page load count.
+  void ResetPageLoads();
+
+  // Size of |evicted_tabs_|.  Used for testing.
+  int EvictedTabsMapSize();
+
+  // Resets all tracked data.  Used for testing.
+  void ResetAll();
+
+  // Sets the delegate for the TabUsageRecorder.
+  void SetDelegate(id<TabUsageRecorderDelegate> delegate);
+
+ protected:
+  // Keep track of when the most recent tab restore begins, to record the time
+  // between evicted-tab-reloads.
+  base::TimeTicks restore_start_time_;
+
+  // Keep track of the timestamps of renderer terminations in order to find the
+  // number of recently alive tabs when a renderer termination occurs.
+  std::deque<base::TimeTicks> termination_timestamps_;
+
+ private:
+  // Clear out all state regarding a current evicted tab.
+  void ResetEvictedTab();
+
+  // Whether or not a tab can be disregarded by the metrics.
+  bool ShouldIgnoreTab(Tab* tab);
+
+  // Whether or not the tab has already been evicted.
+  bool TabAlreadyEvicted(Tab* tab);
+
+  // Returns the state of the given tab.  Call only once per tab, as it removes
+  // the tab from |evicted_tabs_|.
+  TabStateWhenSelected ExtractTabState(Tab* tab);
+
+  // Records various time metrics when a restore of an evicted tab begins.
+  void RecordRestoreStartTime();
+
+  // Clears deleted tabs from |evicted_tabs_|.
+  void ClearDeletedTabs();
+
+  // Number of page loads since the last evicted tab was seen.
+  unsigned int page_loads_;
+
+  // Keep track of the current tab, but only if it has been evicted.
+  // This is kept as a pointer value only - it should never be dereferenced.
+  void* evicted_tab_;
+
+  // State of |evicted_tab_| at the time it became the current tab.
+  TabStateWhenSelected evicted_tab_state_;
+
+  // Keep track of the tab last selected when this tab model was switched
+  // away from to another mode (e.g. to incognito).
+  // Kept as a pointer value only - it should never be dereferenced.
+  void* mode_switch_tab_;
+
+  // Keep track of a tab that was created to be immediately selected.  It should
+  // not contribute to the "StatusWhenSwitchedBackToForeground" metric.
+  void* tab_created_selected_;
+
+  // Keep track of when the evicted tab starts to reload, so that the total
+  // time it takes to reload can be recorded.
+  base::TimeTicks evicted_tab_reload_start_time_;
+
+  // Keep track of the tabs that have a known eviction cause.
+  std::map<base::WeakNSObject<Tab>, TabStateWhenSelected> evicted_tabs_;
+
+  // Reference to TabUsageRecorderDelegate which provides access to the count of
+  // live tabs monitored by this recorder.
+  base::WeakNSProtocol<id<TabUsageRecorderDelegate>> recorder_delegate_;
+
+  DISALLOW_COPY_AND_ASSIGN(TabUsageRecorder);
+};
+
+#endif  // IOS_CHROME_BROWSER_METRICS_TAB_USAGE_RECORDER_H_