Implement pressing back button and swiping back

This CL implements a pressBack function to press back button or swiping
back in gesture navigation mode.

Bug: 199120092
Test: atest -c Launcher3Tests:com.android.launcher3.ui.TaplTestsLauncher3#testPressBack &&
    atest -c NexusLauncherTests:com.android.quickstep.TaplTestsQuickstep#testPressBack
Change-Id: I001cea17d09ae1ab7952d04ee394a2afa5bf1e67

quickstep/tests/src/com/android/quickstep/TaplTestsQuickstep.java

@@ -31,6 +31,7 @@ import androidx.test.uiautomator.Until;
 
 import com.android.launcher3.Launcher;
 import com.android.launcher3.LauncherState;
+import com.android.launcher3.tapl.AllApps;
 import com.android.launcher3.tapl.Background;
 import com.android.launcher3.tapl.LauncherInstrumentation.NavigationModel;
 import com.android.launcher3.tapl.Overview;
@@ -49,6 +50,9 @@ import org.junit.runner.RunWith;
 @LargeTest
 @RunWith(AndroidJUnit4.class)
 public class TaplTestsQuickstep extends AbstractQuickStepTest {
+
+    private static final String APP_NAME = "LauncherTestApp";
+
     @Before
     public void setUp() throws Exception {
         super.setUp();
@@ -286,6 +290,30 @@ public class TaplTestsQuickstep extends AbstractQuickStepTest {
         getAndAssertBackground();
     }
 
+    // TODO(b/204830798): test with all navigation modes(add @NavigationModeSwitch annotation)
+    //  after the bug resolved.
+    @Test
+    @PortraitLandscape
+    @ScreenRecord
+    public void testPressBack() throws Exception {
+        mLauncher.getWorkspace().switchToAllApps();
+        mLauncher.pressBack();
+        mLauncher.getWorkspace();
+        waitForState("Launcher internal state didn't switch to Home", () -> LauncherState.NORMAL);
+
+        AllApps allApps = mLauncher.getWorkspace().switchToAllApps();
+        allApps.freeze();
+        try {
+            allApps.getAppIcon(APP_NAME).dragToWorkspace(false, false);
+        } finally {
+            allApps.unfreeze();
+        }
+        mLauncher.getWorkspace().getWorkspaceAppIcon(APP_NAME).launch(getAppPackageName());
+        mLauncher.pressBack();
+        mLauncher.getWorkspace();
+        waitForState("Launcher internal state didn't switch to Home", () -> LauncherState.NORMAL);
+    }
+
     @Test
     @PortraitLandscape
     public void testOverviewForTablet() throws Exception {