[StartSurface] Hide the top tab switcher toolbar on the explore surface

The screenshot:
https://drive.google.com/file/d/1hFwKWKo8fVp9BvxX6i7FClsguEidiXZs/view?usp=sharing

Bug: 982018
Change-Id: I4901d1e5dc34540c0d445ec5f73fc1017a1abef4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1724652
Auto-Submit: Ganggui Tang <gogerald@chromium.org>
Reviewed-by: Yusuf Ozuysal <yusufo@chromium.org>
Commit-Queue: Ganggui Tang <gogerald@chromium.org>
Cr-Commit-Position: refs/heads/master@{#681820}

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

@@ -7,6 +7,8 @@ package org.chromium.chrome.features.start_surface;
 import static org.chromium.chrome.features.start_surface.StartSurfaceProperties.BOTTOM_BAR_HEIGHT;
 import static org.chromium.chrome.features.start_surface.StartSurfaceProperties.TOP_BAR_HEIGHT;
 
+import android.view.ViewGroup;
+
 import org.chromium.base.ContextUtils;
 import org.chromium.chrome.browser.ChromeActivity;
 import org.chromium.chrome.browser.ChromeFeatureList;
@@ -47,8 +49,8 @@ public class StartSurfaceCoordinator implements StartSurface {
             int singleToolbarHeight =
                     activity.getResources().getDimensionPixelSize(R.dimen.toolbar_height_no_shadow);
             int toolbarHeight = ReturnToChromeExperimentsUtil.shouldShowOmniboxOnTabSwitcher()
-                    ? singleToolbarHeight * 2
-                    : singleToolbarHeight;
+                    ? singleToolbarHeight
+                    : 0;
             mPropertyModel.set(TOP_BAR_HEIGHT, toolbarHeight);
 
             // Create the bottom bar.
@@ -56,8 +58,12 @@ public class StartSurfaceCoordinator implements StartSurface {
                     activity, activity.getCompositorViewHolder(), mPropertyModel);
 
             // Create the explore surface.
+            // TODO(crbug.com/982018): This is a hack to hide the top tab switcher toolbar in
+            // the explore surface. Remove it after deciding on where to put the omnibox.
+            ViewGroup exploreSurfaceContainer =
+                    (ViewGroup) activity.getCompositorViewHolder().getParent();
             mExploreSurfaceCoordinator = new ExploreSurfaceCoordinator(
-                    activity, activity.getCompositorViewHolder(), mPropertyModel);
+                    activity, exploreSurfaceContainer, mPropertyModel);
         }
 
         mStartSurfaceMediator = new StartSurfaceMediator(mGridTabSwitcher.getGridController(),