[iOS] Reset FullscreenModel when the active WebState changes.

Bug: 799101
Cq-Include-Trybots: master.tryserver.chromium.mac:ios-simulator-cronet;master.tryserver.chromium.mac:ios-simulator-full-configs
Change-Id: If760fdaf17dfe79b54510c0eaa2e670dfb326a2c
Reviewed-on: https://chromium-review.googlesource.com/882665
Commit-Queue: Kurt Horimoto <kkhorimoto@chromium.org>
Reviewed-by: Justin Cohen <justincohen@chromium.org>
Reviewed-by: Sergio Collazos <sczs@chromium.org>
Cr-Commit-Position: refs/heads/master@{#532676}

ios/chrome/browser/ui/fullscreen/fullscreen_web_state_list_observer_unittest.mm

@@ -32,7 +32,6 @@ class FullscreenWebStateListObserverTest : public PlatformTest {
         mediator_(&controller_, &model_),
         web_state_list_(&web_state_list_delegate_),
         observer_(&controller_, &model_, &web_state_list_, &mediator_) {
-    SetUpFullscreenModelForTesting(&model_, 100.0);
   }
 
   ~FullscreenWebStateListObserverTest() override {
@@ -62,6 +61,7 @@ TEST_F(FullscreenWebStateListObserverTest, ObserveActiveWebState) {
                                   WebStateList::INSERT_ACTIVATE,
                                   WebStateOpener());
   // Simulate a scroll to 0.5 progress.
+  SetUpFullscreenModelForTesting(&model(), 100.0);
   SimulateFullscreenUserScrollForProgress(&model(), 0.5);
   EXPECT_EQ(model().progress(), 0.5);
   // Simulate a navigation.  The model should be reset by the observers.

ios/chrome/browser/ui/fullscreen/fullscreen_web_state_observer.mm

@@ -57,8 +57,11 @@ void FullscreenWebStateObserver::SetWebState(web::WebState* web_state) {
   if (web_state_)
     web_state_->RemoveObserver(this);
   web_state_ = web_state;
-  if (web_state_)
+  if (web_state_) {
     web_state_->AddObserver(this);
+    // The toolbar should be visible whenever the current tab changes.
+    model_->ResetForNavigation();
+  }
   // Update the model according to the new WebState.
   SetIsLoading(web_state_ ? web_state->IsLoading() : false);
   SetDisableFullscreenForSSL(ShouldDisableFullscreenForWebStateSSL(web_state_));

ios/chrome/browser/ui/fullscreen/fullscreen_web_state_observer_unittest.mm

@@ -26,8 +26,6 @@ class FullscreenWebStateObserverTest : public PlatformTest {
         controller_(&model_),
         mediator_(&controller_, &model_),
         observer_(&controller_, &model_, &mediator_) {
-    // Set up model.
-    SetUpFullscreenModelForTesting(&model_, 100.0);
     // Set up a TestNavigationManager.
     std::unique_ptr<web::TestNavigationManager> navigation_manager =
         std::make_unique<web::TestNavigationManager>();
@@ -35,6 +33,8 @@ class FullscreenWebStateObserverTest : public PlatformTest {
     web_state_.SetNavigationManager(std::move(navigation_manager));
     // Begin observing the WebState.
     observer_.SetWebState(&web_state_);
+    // Set up model.
+    SetUpFullscreenModelForTesting(&model_, 100.0);
   }
 
   ~FullscreenWebStateObserverTest() override {