[Start Surface] Show on swipe down from locationbar.

Follow up to:
https://chromium-review.googlesource.com/c/chromium/src/+/1956187

Before: StartSurface state is not shown correctly when triggered through swipe down,
because StartSurface state is not set in LayoutManager.
StartSurface state is not always set in Activity.

After:
If state is not set (on swipe down), StartSurface defaults to SHOWING_HOME.
Start Surface state is always set correctly in ChromeTabbedActivity.

Bug: 1038276, 1038274
Change-Id: Ifbf7ece713a6866b2c9925d485f1ae3a27d24d51
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1981096
Commit-Queue: Mia Glaese <glamia@chromium.org>
Reviewed-by: Yusuf Ozuysal <yusufo@chromium.org>
Reviewed-by: Ganggui Tang <gogerald@chromium.org>
Cr-Commit-Position: refs/heads/master@{#728329}

chrome/android/features/start_surface/internal/java/src/org/chromium/chrome/features/start_surface/StartSurfaceMediator.java

@@ -359,9 +359,16 @@ class StartSurfaceMediator
             mIsIncognito = mTabModelSelector.isIncognitoSelected();
             mPropertyModel.set(IS_INCOGNITO, mIsIncognito);
 
+            // if OvervieModeState is NOT_SHOWN, default to SHOWING_HOMEPAGE. This should only
+            // happen when entering Start through SwipeDown gesture on URL bar.
+            if (mOverviewModeState == OverviewModeState.NOT_SHOWN) {
+                mOverviewModeState = OverviewModeState.SHOWING_HOMEPAGE;
+            }
+
             // set OverviewModeState
             @OverviewModeState
             int shownState = computeOverviewStateShown();
+            assert (isShownState(shownState));
             setOverviewState(shownState);
 
             // Make sure FeedSurfaceCoordinator is built before the explore surface is showing by

chrome/android/features/start_surface/internal/junit/src/org/chromium/chrome/features/start_surface/StartSurfaceMediatorUnitTest.java

@@ -958,6 +958,59 @@ public class StartSurfaceMediatorUnitTest {
         assertThat(mediator.shouldShowTabSwitcherToolbar(), equalTo(true));
     }
 
+    @Test
+    public void defaultStateSinglePane() {
+        doReturn(false).when(mTabModelSelector).isIncognitoSelected();
+        doReturn(mLocationBarVoiceRecognitionHandler)
+                .when(mFakeBoxDelegate)
+                .getLocationBarVoiceRecognitionHandler();
+        doReturn(true).when(mLocationBarVoiceRecognitionHandler).isVoiceSearchEnabled();
+
+        StartSurfaceMediator mediator = createStartSurfaceMediator(SurfaceMode.SINGLE_PANE);
+        verify(mMainTabGridController)
+                .addOverviewModeObserver(mOverviewModeObserverCaptor.capture());
+
+        assertThat(mediator.getOverviewState(), equalTo(OverviewModeState.NOT_SHOWN));
+        mediator.showOverview(false);
+        assertThat(mediator.getOverviewState(), equalTo(OverviewModeState.SHOWN_HOMEPAGE));
+    }
+
+    @Test
+    public void defaultStateTaskOnly() {
+        doReturn(false).when(mTabModelSelector).isIncognitoSelected();
+        doReturn(mLocationBarVoiceRecognitionHandler)
+                .when(mFakeBoxDelegate)
+                .getLocationBarVoiceRecognitionHandler();
+        doReturn(true).when(mLocationBarVoiceRecognitionHandler).isVoiceSearchEnabled();
+
+        StartSurfaceMediator mediator = createStartSurfaceMediator(SurfaceMode.TASKS_ONLY);
+        verify(mMainTabGridController)
+                .addOverviewModeObserver(mOverviewModeObserverCaptor.capture());
+
+        assertThat(mediator.getOverviewState(), equalTo(OverviewModeState.NOT_SHOWN));
+        mediator.showOverview(false);
+        assertThat(mediator.getOverviewState(),
+                equalTo(OverviewModeState.SHOWN_TABSWITCHER_TASKS_ONLY));
+    }
+
+    @Test
+    public void defaultStateTwoPanes() {
+        doReturn(false).when(mTabModelSelector).isIncognitoSelected();
+        doReturn(mLocationBarVoiceRecognitionHandler)
+                .when(mFakeBoxDelegate)
+                .getLocationBarVoiceRecognitionHandler();
+        doReturn(true).when(mLocationBarVoiceRecognitionHandler).isVoiceSearchEnabled();
+
+        StartSurfaceMediator mediator = createStartSurfaceMediator(SurfaceMode.TWO_PANES);
+        verify(mMainTabGridController)
+                .addOverviewModeObserver(mOverviewModeObserverCaptor.capture());
+
+        assertThat(mediator.getOverviewState(), equalTo(OverviewModeState.NOT_SHOWN));
+        mediator.showOverview(false);
+        assertThat(mediator.getOverviewState(),
+                equalTo(OverviewModeState.SHOWN_TABSWITCHER_TWO_PANES));
+    }
+
     @Test
     public void showAndHideTabSwitcherToolbarTabswitcher() {
         doReturn(false).when(mTabModelSelector).isIncognitoSelected();

chrome/android/java/src/org/chromium/chrome/browser/ChromeTabbedActivity.java

@@ -1879,7 +1879,7 @@ public class ChromeTabbedActivity extends ChromeActivity implements ScreenshotMo
                 getCurrentTabModel().closeTab(tabToClose, false, true, false);
 
                 // If there is no next tab to open, enter overview mode.
-                if (!hasNextTab) mOverviewModeController.showOverview(false);
+                if (!hasNextTab) showOverview(OverviewModeState.SHOWING_START);
             }, CLOSE_TAB_ON_MINIMIZE_DELAY_MS);
         }
     }