Fix TabGroupModelFilter casting exception

TabUiFeatureUtilities.isTabGroupsAndroidEnabled() does not guarantee
TabModelFilterProvider().getTabModelFilter() returns
TabGroupModelFilter. It can return null before
TabModelSelectorBase#initialize() is called. This CL early returns when
TabModelFilterProvider().getTabModelFilter() is not a
TabGroupModelFilter to avoid the casting exception.

This CL is gated by Finch parameter "enable_launch_polish" under flag
"enable-tab-grid-layout", with gate function
TabUiFeatureUtilities#isLaunchPolishEnabled.

Bug: 1133922
Change-Id: I9766d4f0f54c954f8205866aa0c514b508d7a5a0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2442479
Commit-Queue: Mei Liang <meiliang@chromium.org>
Reviewed-by: Wei-Yin Chen (陳威尹) <wychen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#812865}

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

@@ -23,6 +23,7 @@ import org.chromium.chrome.browser.lifecycle.PauseResumeWithNativeObserver;
 import org.chromium.chrome.browser.metrics.UmaSessionStats;
 import org.chromium.chrome.browser.tab.Tab;
 import org.chromium.chrome.browser.tab.state.CriticalPersistedTabData;
+import org.chromium.chrome.browser.tabmodel.TabModelFilter;
 import org.chromium.chrome.browser.tabmodel.TabModelFilterProvider;
 import org.chromium.chrome.browser.tabmodel.TabModelObserver;
 import org.chromium.chrome.browser.tabmodel.TabModelSelector;
@@ -126,7 +127,7 @@ public class TabGroupUiCoordinator implements TabGroupUiMediator.ResetHandler, T
         mActivityLifecycleDispatcher = activity.getLifecycleDispatcher();
         mActivityLifecycleDispatcher.register(this);
 
-
+        // TODO(meiliang): Potential leak if the observer is added after restoreCompleted. Fix it.
         // Record the group count after all tabs are being restored. This only happen once per life
         // cycle, therefore remove the observer after recording. We only focus on normal tab model
         // because we don't restore tabs in incognito tab model.
@@ -214,6 +215,22 @@ public class TabGroupUiCoordinator implements TabGroupUiMediator.ResetHandler, T
     private void recordTabGroupCount() {
         TabModelFilterProvider provider =
                 mActivity.getTabModelSelector().getTabModelFilterProvider();
+
+        if (TabUiFeatureUtilities.isLaunchPolishEnabled()) {
+            TabModelFilter normalTabModelFilter = provider.getTabModelFilter(false);
+
+            if (!(normalTabModelFilter instanceof TabGroupModelFilter)) {
+                String actualType = normalTabModelFilter == null
+                        ? "null"
+                        : normalTabModelFilter.getClass().getName();
+                assert false
+                    : "Please file bug, this is unexpected. Expected TabGroupModelFilter, but was "
+                      + actualType;
+
+                return;
+            }
+        }
+
         TabGroupModelFilter normalFilter = (TabGroupModelFilter) provider.getTabModelFilter(false);
         TabGroupModelFilter incognitoFilter =
                 (TabGroupModelFilter) provider.getTabModelFilter(true);