[Start] Show tab switcher as SwipeDown gesture on URL bar.

Bug: 1121728
Change-Id: Ib2b0c0dcf9ddccfdb9408d2b219c579da083241d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2398898
Commit-Queue: Xi Han <hanxi@chromium.org>
Reviewed-by: Wei-Yin Chen (陳威尹) <wychen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#805741}

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

@@ -531,10 +531,10 @@ class StartSurfaceMediator
             mIsIncognito = mTabModelSelector.isIncognitoSelected();
             mPropertyModel.set(IS_INCOGNITO, mIsIncognito);
 
-            // if OvervieModeState is NOT_SHOWN, default to SHOWING_HOMEPAGE. This should only
+            // if OvervieModeState is NOT_SHOWN, default to SHOWING_TABSWITCHER. This should only
             // happen when entering Start through SwipeDown gesture on URL bar.
             if (mOverviewModeState == OverviewModeState.NOT_SHOWN) {
-                mOverviewModeState = OverviewModeState.SHOWING_HOMEPAGE;
+                mOverviewModeState = OverviewModeState.SHOWING_TABSWITCHER;
             }
 
             // set OverviewModeState
@@ -744,9 +744,11 @@ class StartSurfaceMediator
             if (mSecondaryTasksSurfacePropertyModel == null) {
                 mSecondaryTasksSurfaceController = mSecondaryTasksSurfaceInitializer.initialize();
             }
-            mSecondaryTasksSurfacePropertyModel.set(IS_FAKE_SEARCH_BOX_VISIBLE,
-                    mIsIncognito && mOverviewModeState == OverviewModeState.SHOWN_HOMEPAGE);
-            mSecondaryTasksSurfacePropertyModel.set(IS_INCOGNITO, mIsIncognito);
+            if (mSecondaryTasksSurfacePropertyModel != null) {
+                mSecondaryTasksSurfacePropertyModel.set(IS_FAKE_SEARCH_BOX_VISIBLE,
+                        mIsIncognito && mOverviewModeState == OverviewModeState.SHOWN_HOMEPAGE);
+                mSecondaryTasksSurfacePropertyModel.set(IS_INCOGNITO, mIsIncognito);
+            }
             if (mSecondaryTasksSurfaceController != null) {
                 mSecondaryTasksSurfaceController.showOverview(false);
             }

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

@@ -323,6 +323,11 @@ public class StartSurfaceMediatorUnitTest {
                 .addOverviewModeObserver(mOverviewModeObserverCaptor.capture());
 
         assertThat(mediator.getOverviewState(), equalTo(OverviewModeState.NOT_SHOWN));
+        // Sets the current OvervieModeState to SHOWING_START before calling the
+        // {@link StartSurfaceMediator#showOverview()}. This is because if the current
+        // OvervieModeState is NOT_SHOWN, the state will be set default to SHOWING_TABSWITCHER in
+        // {@link StartSurfaceMediator#showOverview()}.
+        mediator.setOverviewState(OverviewModeState.SHOWING_START);
 
         mediator.showOverview(false);
         verify(mMainTabGridController).showOverview(eq(false));
@@ -368,6 +373,11 @@ public class StartSurfaceMediatorUnitTest {
                 .addOverviewModeObserver(mOverviewModeObserverCaptor.capture());
 
         assertThat(mediator.getOverviewState(), equalTo(OverviewModeState.NOT_SHOWN));
+        // Sets the current OvervieModeState to SHOWING_START before calling the
+        // {@link StartSurfaceMediator#showOverview()}. This is because if the current
+        // OvervieModeState is NOT_SHOWN, the state will be set default to SHOWING_TABSWITCHER in
+        // {@link StartSurfaceMediator#showOverview()}.
+        mediator.setOverviewState(OverviewModeState.SHOWING_START);
 
         mediator.showOverview(false);
         verify(mMainTabGridController).showOverview(eq(false));
@@ -414,6 +424,11 @@ public class StartSurfaceMediatorUnitTest {
                 .addOverviewModeObserver(mOverviewModeObserverCaptor.capture());
 
         assertThat(mediator.getOverviewState(), equalTo(OverviewModeState.NOT_SHOWN));
+        // Sets the current OvervieModeState to SHOWING_START before calling the
+        // {@link StartSurfaceMediator#showOverview()}. This is because if the current
+        // OvervieModeState is NOT_SHOWN, the state will be set default to SHOWING_TABSWITCHER in
+        // {@link StartSurfaceMediator#showOverview()}.
+        mediator.setOverviewState(OverviewModeState.SHOWING_START);
 
         mediator.showOverview(false);
         verify(mMainTabGridController).showOverview(eq(false));
@@ -1364,7 +1379,7 @@ public class StartSurfaceMediatorUnitTest {
 
         assertThat(mediator.getOverviewState(), equalTo(OverviewModeState.NOT_SHOWN));
         mediator.showOverview(false);
-        assertThat(mediator.getOverviewState(), equalTo(OverviewModeState.SHOWN_HOMEPAGE));
+        assertThat(mediator.getOverviewState(), equalTo(OverviewModeState.SHOWN_TABSWITCHER));
     }
 
     @Test
@@ -1500,6 +1515,11 @@ public class StartSurfaceMediatorUnitTest {
                 .when(mBrowserControlsStateProvider)
                 .addObserver(mBrowserControlsStateProviderCaptor.capture());
         StartSurfaceMediator mediator = createStartSurfaceMediator(SurfaceMode.SINGLE_PANE, false);
+        // Sets the current OvervieModeState to SHOWING_START before calling the
+        // {@link StartSurfaceMediator#showOverview()}. This is because if the current
+        // OvervieModeState is NOT_SHOWN, the state will be set default to SHOWING_TABSWITCHER in
+        // {@link StartSurfaceMediator#showOverview()}.
+        mediator.setOverviewState(OverviewModeState.SHOWING_START);
         mediator.showOverview(false);
 
         verify(mBrowserControlsStateProvider).addObserver(ArgumentMatchers.any());
@@ -1527,6 +1547,11 @@ public class StartSurfaceMediatorUnitTest {
                 .addOverviewModeObserver(mOverviewModeObserverCaptor.capture());
 
         assertThat(mediator.getOverviewState(), equalTo(OverviewModeState.NOT_SHOWN));
+        // Sets the current OvervieModeState to SHOWING_START before calling the
+        // {@link StartSurfaceMediator#showOverview()}. This is because if the current
+        // OvervieModeState is NOT_SHOWN, the state will be set default to SHOWING_TABSWITCHER in
+        // {@link StartSurfaceMediator#showOverview()}.
+        mediator.setOverviewState(OverviewModeState.SHOWING_START);
         mediator.showOverview(false);
         assertThat(mediator.getOverviewState(), equalTo(OverviewModeState.SHOWN_HOMEPAGE));
         assertThat(mPropertyModel.get(IS_EXPLORE_SURFACE_VISIBLE), equalTo(false));