Properly update tab strip for tab selection

Currently, when user uses swipe gesture to switch from a single tab to
a tab in tab group, the tab strip doesn't show up. This is due to this
tab selection doesn't fire a reset tab strip event. This CL fixes this
issue and adds tests.

Bug: 1048824
Change-Id: I05ad51709eb6274afc41f4fc6ddbd8ce396640a4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2037844Reviewed-by: Wei-Yin Chen (陳威尹) <wychen@chromium.org>
Commit-Queue: Yue Zhang <yuezhanggg@chromium.org>
Cr-Commit-Position: refs/heads/master@{#738391}

chrome/android/features/tab_ui/java/src/org/chromium/chrome/browser/tasks/tab_management/TabGroupUiMediator.java

@@ -117,7 +117,6 @@ public class TabGroupUiMediator {
         mTabModelObserver = new EmptyTabModelObserver() {
             @Override
             public void didSelectTab(Tab tab, @TabSelectionType int type, int lastId) {
-                if (!mIsTabGroupUiVisible) return;
                 if (type == TabSelectionType.FROM_CLOSE) return;
                 if (getRelatedTabsForId(lastId).contains(tab)) return;
                 // TODO(995956): Optimization we can do here if we decided always hide the strip if

chrome/android/features/tab_ui/junit/src/org/chromium/chrome/browser/tasks/tab_management/TabGroupUiMediatorUnitTest.java

@@ -335,7 +335,7 @@ public class TabGroupUiMediatorUnitTest {
     }
 
     @Test
-    public void tabSelection_NotSameGroup_SingleTab() {
+    public void tabSelection_NotSameGroup_GroupToSingleTab() {
         initAndAssertProperties(mTab2);
 
         // Mock selecting tab 1, and the last selected tab is tab 2 which is in different group.
@@ -347,7 +347,7 @@ public class TabGroupUiMediatorUnitTest {
     }
 
     @Test
-    public void tabSelection_NotSameGroup_TabGroup() {
+    public void tabSelection_NotSameGroup_GroupToGroup() {
         initAndAssertProperties(mTab2);
 
         // Mock that tab 1 is not a single tab.
@@ -363,6 +363,39 @@ public class TabGroupUiMediatorUnitTest {
         verifyResetStrip(true, tabs);
     }
 
+    @Test
+    public void tabSelection_NotSameGroup_SingleTabToGroup() {
+        initAndAssertProperties(mTab1);
+
+        // Mock that tab 2 is not a single tab.
+        List<Tab> tabGroup = mTabGroupModelFilter.getRelatedTabList(TAB2_ID);
+        assertThat(tabGroup.size(), equalTo(2));
+
+        // Mock selecting tab 2, and the last selected tab is tab 1 which is a single tab.
+        mTabModelObserverArgumentCaptor.getValue().didSelectTab(
+                mTab2, TabSelectionType.FROM_USER, TAB1_ID);
+
+        // Strip should be showing since we are selecting a group.
+        verifyResetStrip(true, tabGroup);
+    }
+
+    @Test
+    public void tabSelection_NotSameGroup_SingleTabToSingleTab() {
+        initAndAssertProperties(mTab1);
+
+        // Mock that new tab is a single tab.
+        TabImpl newTab = prepareTab(TAB4_ID, TAB4_ID);
+        List<Tab> tabs = new ArrayList<>(Arrays.asList(newTab));
+        doReturn(tabs).when(mTabGroupModelFilter).getRelatedTabList(TAB4_ID);
+
+        // Mock selecting new tab, and the last selected tab is tab 1 which is also a single tab.
+        mTabModelObserverArgumentCaptor.getValue().didSelectTab(
+                newTab, TabSelectionType.FROM_USER, TAB1_ID);
+
+        // Strip should not be showing since new tab is a single tab.
+        verifyResetStrip(false, null);
+    }
+
     @Test
     public void tabSelection_SameGroup_TabGroup() {
         initAndAssertProperties(mTab2);