Revert of [ios] Move WebStateList to ios/chrome/browser/web_state_list.

ios/chrome/browser/web_state_list/web_state_list_metrics_observer.mm

Index: ios/chrome/browser/web_state_list/web_state_list_metrics_observer.mm
diff --git a/ios/chrome/browser/web_state_list/web_state_list_metrics_observer.mm b/ios/chrome/browser/web_state_list/web_state_list_metrics_observer.mm
deleted file mode 100644
index a29f776f53e998e2a37160cbad86c22d7a4802fb..0000000000000000000000000000000000000000
--- a/ios/chrome/browser/web_state_list/web_state_list_metrics_observer.mm
+++ /dev/null
@@ -1,73 +0,0 @@
-// Copyright 2017 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.
-
-#import "ios/chrome/browser/web_state_list/web_state_list_metrics_observer.h"
-
-#include "base/metrics/histogram_macros.h"
-#include "base/metrics/user_metrics.h"
-#include "base/metrics/user_metrics_action.h"
-
-#if !defined(__has_feature) || !__has_feature(objc_arc)
-#error "This file requires ARC support."
-#endif
-
-WebStateListMetricsObserver::WebStateListMetricsObserver() {
-  ResetSessionMetrics();
-}
-
-WebStateListMetricsObserver::~WebStateListMetricsObserver() = default;
-
-void WebStateListMetricsObserver::ResetSessionMetrics() {
-  inserted_web_state_counter_ = 0;
-  detached_web_state_counter_ = 0;
-  activated_web_state_counter_ = 0;
-}
-
-void WebStateListMetricsObserver::RecordSessionMetrics() {
-  UMA_HISTOGRAM_CUSTOM_COUNTS("Session.ClosedTabCounts",
-                              detached_web_state_counter_, 1, 200, 50);
-  UMA_HISTOGRAM_CUSTOM_COUNTS("Session.OpenedTabCounts",
-                              activated_web_state_counter_, 1, 200, 50);
-  UMA_HISTOGRAM_CUSTOM_COUNTS("Session.NewTabCounts",
-                              inserted_web_state_counter_, 1, 200, 50);
-}
-
-void WebStateListMetricsObserver::WebStateInsertedAt(
-    WebStateList* web_state_list,
-    web::WebState* web_state,
-    int index) {
-  base::RecordAction(base::UserMetricsAction("MobileNewTabOpened"));
-  ++inserted_web_state_counter_;
-}
-
-void WebStateListMetricsObserver::WebStateReplacedAt(
-    WebStateList* web_state_list,
-    web::WebState* old_web_state,
-    web::WebState* new_web_state,
-    int index) {
-  // Record a tab clobber, since swapping tabs bypasses the Tab code that would
-  // normally log clobbers.
-  base::RecordAction(base::UserMetricsAction("MobileTabClobbered"));
-}
-
-void WebStateListMetricsObserver::WebStateDetachedAt(
-    WebStateList* web_state_list,
-    web::WebState* web_state,
-    int index) {
-  base::RecordAction(base::UserMetricsAction("MobileTabClosed"));
-  ++detached_web_state_counter_;
-}
-
-void WebStateListMetricsObserver::WebStateActivatedAt(
-    WebStateList* web_state_list,
-    web::WebState* old_web_state,
-    web::WebState* new_web_state,
-    int active_index,
-    bool user_action) {
-  ++activated_web_state_counter_;
-  if (!user_action)
-    return;
-
-  base::RecordAction(base::UserMetricsAction("MobileTabSwitched"));
-}