[ios] Call SnapshotTabHelper instead of SnapshotBrowserAgent in TabModel

The calls to SnapshotCache methods via SnapshotBrowserAgent required
obtaining and passing in a Tab ID. It is more correct to directly
call the SnapshotTabHelper since it is tied to the WebState.

Change-Id: Ie0a7f1976544bc860e4b0cf4ba4e4e381689333e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2370015Reviewed-by: Mark Cogan <marq@chromium.org>
Commit-Queue: edchin <edchin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#801385}

ios/chrome/browser/snapshots/snapshot_cache.h

@@ -78,6 +78,7 @@ class Time;
 // background thread.
 - (void)purgeCacheOlderThan:(const base::Time&)date
                     keeping:(NSSet*)liveSnapshotIDs;
+
 // Hint that the snapshot for |snapshotID| will likely be saved to disk when the
 // application is backgrounded.  The snapshot is then saved in memory, so it
 // does not need to be read off disk.

ios/chrome/browser/snapshots/snapshot_tab_helper.h

@@ -78,6 +78,15 @@ class SnapshotTabHelper : public infobars::InfoBarManager::Observer,
   // Instructs the helper not to snapshot content for the next page load event.
   void IgnoreNextLoad();
 
+  // Hint that the snapshot will likely be saved to disk when the application is
+  // backgrounded.  The snapshot is then saved in memory, so it does not need to
+  // be read off disk.
+  void WillBeSavedGreyWhenBackgrounding();
+
+  // Write a grey copy of the snapshot to disk, but if and only if a color
+  // version of the snapshot already exists in memory or on disk.
+  void SaveGreyInBackground();
+
  private:
   friend class web::WebStateUserData<SnapshotTabHelper>;
 
@@ -97,6 +106,7 @@ class SnapshotTabHelper : public infobars::InfoBarManager::Observer,
   void OnManagerShuttingDown(infobars::InfoBarManager* manager) override;
 
   web::WebState* web_state_ = nullptr;
+  NSString* tab_id_ = nil;
   SnapshotGenerator* snapshot_generator_ = nil;
   infobars::InfoBarManager* infobar_manager_ = nullptr;
 

ios/chrome/browser/snapshots/snapshot_tab_helper.mm

@@ -11,6 +11,7 @@
 #include "components/infobars/core/infobar.h"
 #include "components/infobars/core/infobar_delegate.h"
 #include "ios/chrome/browser/infobars/infobar_manager_impl.h"
+#import "ios/chrome/browser/snapshots/snapshot_cache.h"
 #import "ios/chrome/browser/snapshots/snapshot_generator.h"
 #import "ios/chrome/browser/ui/infobars/infobar_feature.h"
 #include "ios/chrome/browser/ui/util/ui_util.h"
@@ -101,7 +102,6 @@ UIImage* SnapshotTabHelper::GenerateSnapshotWithoutOverlays() {
 }
 
 void SnapshotTabHelper::RemoveSnapshot() {
-  DCHECK(web_state_);
   [snapshot_generator_ removeSnapshot];
 }
 
@@ -109,13 +109,24 @@ void SnapshotTabHelper::IgnoreNextLoad() {
   ignore_next_load_ = true;
 }
 
+void SnapshotTabHelper::WillBeSavedGreyWhenBackgrounding() {
+  [snapshot_generator_.snapshotCache willBeSavedGreyWhenBackgrounding:tab_id_];
+}
+
+void SnapshotTabHelper::SaveGreyInBackground() {
+  [snapshot_generator_.snapshotCache saveGreyInBackgroundForSnapshotID:tab_id_];
+}
+
 SnapshotTabHelper::SnapshotTabHelper(web::WebState* web_state, NSString* tab_id)
     : web_state_(web_state),
+      tab_id_([tab_id copy]),
       web_state_observer_(this),
       infobar_observer_(this),
       weak_ptr_factory_(this) {
+  DCHECK(web_state_);
+  DCHECK(tab_id_.length > 0);
   snapshot_generator_ = [[SnapshotGenerator alloc] initWithWebState:web_state_
-                                                              tabID:tab_id];
+                                                              tabID:tab_id_];
   web_state_observer_.Add(web_state_);
 
   // Supports missing InfoBarManager to make testing easier.
@@ -180,6 +191,7 @@ void SnapshotTabHelper::WebStateDestroyed(web::WebState* web_state) {
   DCHECK_EQ(web_state_, web_state);
   web_state_observer_.Remove(web_state);
   web_state_ = nullptr;
+  tab_id_ = nil;
 }
 
 void SnapshotTabHelper::OnInfoBarAdded(infobars::InfoBar* infobar) {

ios/chrome/browser/tabs/tab_model.mm

@@ -35,10 +35,8 @@
 #import "ios/chrome/browser/sessions/session_restoration_browser_agent.h"
 #import "ios/chrome/browser/sessions/session_service_ios.h"
 #import "ios/chrome/browser/sessions/session_window_ios.h"
-#import "ios/chrome/browser/snapshots/snapshot_browser_agent.h"
-#import "ios/chrome/browser/snapshots/snapshot_cache.h"
+#import "ios/chrome/browser/snapshots/snapshot_tab_helper.h"
 #import "ios/chrome/browser/tabs/tab_parenting_observer.h"
-#import "ios/chrome/browser/web/tab_id_tab_helper.h"
 #import "ios/chrome/browser/web_state_list/web_state_list.h"
 #import "ios/chrome/browser/web_state_list/web_state_list_observer.h"
 #import "ios/chrome/browser/web_state_list/web_usage_enabler/web_usage_enabler_browser_agent.h"
@@ -133,9 +131,6 @@ void RecordInterfaceOrientationMetric() {
   // Weak reference to the session restoration agent.
   SessionRestorationBrowserAgent* _sessionRestorationBrowserAgent;
 
-  // Used for saving gray images.
-  SnapshotBrowserAgent* _snapshotBrowserAgent;
-
   // Used to ensure thread-safety of the certificate policy management code.
   base::CancelableTaskTracker _clearPoliciesTaskTracker;
 
@@ -180,8 +175,6 @@ void RecordInterfaceOrientationMetric() {
         SessionRestorationBrowserAgent::FromBrowser(browser);
     _webEnabler = WebUsageEnablerBrowserAgent::FromBrowser(browser);
 
-    _snapshotBrowserAgent = SnapshotBrowserAgent::FromBrowser(browser);
-
     _webStateListObservers.push_back(std::make_unique<TabParentingObserver>());
 
     for (const auto& webStateListObserver : _webStateListObservers)
@@ -239,12 +232,8 @@ void RecordInterfaceOrientationMetric() {
 // TODO(crbug.com/1115611): Move to SceneController.
 - (void)willResignActive:(NSNotification*)notify {
   if (_webEnabler->IsWebUsageEnabled() && _webStateList->GetActiveWebState()) {
-    NSString* tabId =
-        TabIdTabHelper::FromWebState(_webStateList->GetActiveWebState())
-            ->tab_id();
-
-    [_snapshotBrowserAgent->snapshot_cache()
-        willBeSavedGreyWhenBackgrounding:tabId];
+    SnapshotTabHelper::FromWebState(_webStateList->GetActiveWebState())
+        ->WillBeSavedGreyWhenBackgrounding();
   }
 }
 
@@ -268,12 +257,8 @@ void RecordInterfaceOrientationMetric() {
 
   // Write out a grey version of the current website to disk.
   if (_webEnabler->IsWebUsageEnabled() && _webStateList->GetActiveWebState()) {
-    NSString* tabId =
-        TabIdTabHelper::FromWebState(_webStateList->GetActiveWebState())
-            ->tab_id();
-
-    [_snapshotBrowserAgent->snapshot_cache()
-        saveGreyInBackgroundForSnapshotID:tabId];
+    SnapshotTabHelper::FromWebState(_webStateList->GetActiveWebState())
+        ->SaveGreyInBackground();
   }
 }