Log UMA for session restoration time.

Bug: 877671
Cq-Include-Trybots: luci.chromium.try:ios-simulator-cronet;luci.chromium.try:ios-simulator-full-configs
Change-Id: I1ab57a336a1cccd169f311c1d64db813cd4a1250
Reviewed-on: https://chromium-review.googlesource.com/1232615
Commit-Queue: Eugene But <eugenebut@chromium.org>
Reviewed-by: Danyao Wang <danyao@chromium.org>
Cr-Commit-Position: refs/heads/master@{#592994}

ios/web/navigation/wk_based_navigation_manager_impl.h

@@ -20,12 +20,20 @@
 
 @class WKBackForwardListItem;
 
+namespace base {
+class ElapsedTimer;
+}
+
 namespace web {
 class BrowserState;
 class NavigationItem;
 struct Referrer;
 class SessionStorageBuilder;
 
+// Name of UMA histogram to log the time spent on asynchronous session
+// restoration.
+extern const char kRestoreNavigationTime[];
+
 // WKBackForwardList based implementation of NavigationManagerImpl.
 // This class relies on the following WKWebView APIs, defined by the
 // CRWWebViewNavigationProxy protocol:
@@ -243,6 +251,11 @@ class WKBasedNavigationManagerImpl : public NavigationManagerImpl {
   // OnNavigationItemCommitted() callback.
   bool is_restore_session_in_progress_ = false;
 
+  // Non null during the session restoration. Created when session restoration
+  // is started and reset when the restoration is finished. Used to log UMA
+  // histogram that measures session restoration time.
+  std::unique_ptr<base::ElapsedTimer> restoration_timer_;
+
   // The active navigation entry in the restored session. GetVisibleItem()
   // returns this item when |is_restore_session_in_progress_| is true so that
   // clients of this navigation manager gets sane values for visible title and

ios/web/navigation/wk_based_navigation_manager_impl.mm

@@ -10,8 +10,10 @@
 #include "base/logging.h"
 #include "base/mac/bundle_locations.h"
 #include "base/memory/ptr_util.h"
+#include "base/metrics/histogram_macros.h"
 #include "base/strings/string_util.h"
 #include "base/strings/sys_string_conversions.h"
+#include "base/timer/elapsed_timer.h"
 #import "ios/web/navigation/crw_navigation_item_holder.h"
 #import "ios/web/navigation/navigation_item_impl.h"
 #include "ios/web/navigation/navigation_item_impl_list.h"
@@ -57,6 +59,8 @@ bool IsSameOrPlaceholderOf(const GURL& url1, const GURL& url2) {
 
 namespace web {
 
+const char kRestoreNavigationTime[] = "IOS.RestoreNavigationTime";
+
 WKBasedNavigationManagerImpl::WKBasedNavigationManagerImpl()
     : pending_item_index_(-1),
       previous_item_index_(-1),
@@ -88,9 +92,13 @@ void WKBasedNavigationManagerImpl::OnNavigationItemCommitted() {
   details.item = GetLastCommittedItem();
   DCHECK(details.item);
 
-  if (!wk_navigation_util::IsRestoreSessionUrl(details.item->GetURL())) {
+  if (!wk_navigation_util::IsRestoreSessionUrl(details.item->GetURL()) &&
+      is_restore_session_in_progress_) {
     is_restore_session_in_progress_ = false;
     restored_visible_item_.reset();
+
+    UMA_HISTOGRAM_TIMES(kRestoreNavigationTime, restoration_timer_->Elapsed());
+    restoration_timer_.reset();
   }
 
   details.previous_item_index = GetPreviousItemIndex();
@@ -445,6 +453,7 @@ bool WKBasedNavigationManagerImpl::CanPruneAllButLastCommittedItem() const {
 void WKBasedNavigationManagerImpl::Restore(
     int last_committed_item_index,
     std::vector<std::unique_ptr<NavigationItem>> items) {
+  DCHECK(!is_restore_session_in_progress_);
   WillRestore(items.size());
 
   DCHECK_LT(last_committed_item_index, static_cast<int>(items.size()));
@@ -490,6 +499,7 @@ void WKBasedNavigationManagerImpl::Restore(
   // committed item, because a restored session has no pending or transient
   // item.
   is_restore_session_in_progress_ = true;
+  restoration_timer_ = std::make_unique<base::ElapsedTimer>();
   if (last_committed_item_index > -1)
     restored_visible_item_ = std::move(items[last_committed_item_index]);
 

ios/web/web_state/web_state_unittest.mm

@@ -14,6 +14,7 @@
 #include "base/test/scoped_feature_list.h"
 #include "base/values.h"
 #import "ios/web/navigation/navigation_manager_impl.h"
+#import "ios/web/navigation/wk_based_navigation_manager_impl.h"
 #import "ios/web/navigation/wk_navigation_util.h"
 #import "ios/web/public/crw_navigation_item_storage.h"
 #import "ios/web/public/crw_session_storage.h"
@@ -391,6 +392,9 @@ TEST_P(WebStateTest, RestoreLargeSession) {
 
   histogram_tester_.ExpectTotalCount(kRestoreNavigationItemCount, 1);
   histogram_tester_.ExpectBucketCount(kRestoreNavigationItemCount, 100, 1);
+  if (web::GetWebClient()->IsSlimNavigationManagerEnabled()) {
+    histogram_tester_.ExpectTotalCount(kRestoreNavigationTime, 1);
+  }
 }
 
 // Tests that if a saved session is provided when creating a new WebState, it is