Initialize WebStateListMetricsBrowser after SessionRestorationBrowser

WebStateListMetricsBrowser requires SessionRestorationBrowserAgent,
so it must be initialized earlier.

Also initialize WebStateListMetricsBrowser member variables that were
left uninitialized.

Bug: 1132784
Change-Id: I28b9d5afca58870a6273eb1c3b3418a45c9fcd69
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2435344
Commit-Queue: Olivier Robin <olivierrobin@chromium.org>
Auto-Submit: Olivier Robin <olivierrobin@chromium.org>
Reviewed-by: Sylvain Defresne <sdefresne@chromium.org>
Cr-Commit-Position: refs/heads/master@{#811236}

ios/chrome/browser/main/browser_agent_util.mm

@@ -42,6 +42,12 @@ void AttachBrowserAgents(Browser* browser) {
   DeviceSharingBrowserAgent::CreateForBrowser(browser);
   UrlLoadingNotifierBrowserAgent::CreateForBrowser(browser);
   AppLauncherBrowserAgent::CreateForBrowser(browser);
+
+  // SessionRestorartionAgent requires WebUsageEnablerBrowserAgent.
+  SessionRestorationBrowserAgent::CreateForBrowser(
+      browser, [SessionServiceIOS sharedService]);
+
+  // WebStateListMetricsBrowserAgent requires SessionRestorationBrowserAgent.
   WebStateListMetricsBrowserAgent::CreateForBrowser(browser);
   ClosingWebStateObserverBrowserAgent::CreateForBrowser(browser);
   SnapshotBrowserAgent::CreateForBrowser(browser);
@@ -53,10 +59,6 @@ void AttachBrowserAgents(Browser* browser) {
   // UrlLoadingBrowserAgent requires UrlLoadingNotifierBrowserAgent.
   UrlLoadingBrowserAgent::CreateForBrowser(browser);
 
-  // SessionRestorartionAgent requires WebUsageEnablerBrowserAgent.
-  SessionRestorationBrowserAgent::CreateForBrowser(
-      browser, [SessionServiceIOS sharedService]);
-
   // TabUsageRecorderBrowserAgent and WebStateListMetricsBrowserAgent observe
   // the SessionRestorationBrowserAgent, so they should be created after the the
   // SessionRestorationBrowserAgent is created.

ios/chrome/browser/web_state_list/web_state_list_metrics_browser_agent.h

@@ -67,10 +67,10 @@ class WebStateListMetricsBrowserAgent
   WebStateList* web_state_list_;  // weak
 
   // Counters for metrics.
-  int inserted_web_state_counter_;
-  int detached_web_state_counter_;
-  int activated_web_state_counter_;
-  bool metric_collection_paused_;
+  int inserted_web_state_counter_ = 0;
+  int detached_web_state_counter_ = 0;
+  int activated_web_state_counter_ = 0;
+  bool metric_collection_paused_ = false;
 
   DISALLOW_COPY_AND_ASSIGN(WebStateListMetricsBrowserAgent);
 };