Fix SceneState flaky test.

incognitoContentVisible is persisted in NSUserDefaults in some
configurations.
This means that unittests must not assume any initial value and
the value to false (default) if possible.

Change-Id: I4331afe28a60ba1e592d33ca4505af890cb22dc7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2627853
Auto-Submit: Olivier Robin <olivierrobin@chromium.org>
Commit-Queue: Sylvain Defresne <sdefresne@chromium.org>
Reviewed-by: Sylvain Defresne <sdefresne@chromium.org>
Cr-Commit-Position: refs/heads/master@{#843471}

ios/chrome/browser/metrics/incognito_usage_app_state_agent_unittest.mm

@@ -86,6 +86,12 @@ class IncognitoUsageAppStateAgentTest : public PlatformTest {
                 sceneConnected:mock_scene_state2_];
   }
 
+  void TearDown() override {
+    SetScene1DisplaysIncognito(NO);
+    SetScene2DisplaysIncognito(NO);
+    PlatformTest::TearDown();
+  }
+
   base::HistogramTester histogram_tester_;
   base::ScopedMockClockOverride scoped_clock_;
   IncognitoUsageAppStateAgent* incognito_agent_;

ios/chrome/browser/ui/main/incognito_blocker_scene_agent_unittest.mm

@@ -27,6 +27,10 @@ class IncognitoBlockerSceneAgentTest : public PlatformTest {
     agent_.sceneState = scene_state_;
   }
 
+  ~IncognitoBlockerSceneAgentTest() override {
+    scene_state_.incognitoContentVisible = NO;
+  }
+
  protected:
   // The scene state that the agent works with.
   SceneState* scene_state_;

ios/chrome/browser/ui/main/scene_controller_unittest.mm

@@ -32,6 +32,7 @@ class SceneControllerTest : public PlatformTest {
 // Tests that scene controller updates scene state's incognitoContentVisible
 // when the relevant application command is called.
 TEST_F(SceneControllerTest, UpdatesIncognitoContentVisibility) {
+  [scene_controller_ setIncognitoContentVisible:NO];
   EXPECT_FALSE(scene_state_.incognitoContentVisible);
   [scene_controller_ setIncognitoContentVisible:YES];
   EXPECT_TRUE(scene_state_.incognitoContentVisible);