[StartSurface] Fix new tab button color on the start surface in incognito mode

Note that isGridTabSwitcherEnabled is already return true when the
start surface is enabled but not isStartSurfaceStackTabSwitcherEnabled

This CL adds missed changes in
https://chromium-review.googlesource.com/c/chromium/src/+/2173118

Screenshots:
https://drive.google.com/file/d/1WaqU4-N9jYOVC62eMvgOnGlQAwLzJphI/view?usp=sharing
https://drive.google.com/file/d/1uVFGZYEIguGQNlNOWjTSJCHOx5CdBFuK/view?usp=sharing

Bug: 1076449
Change-Id: Ib70134dee8d3e12f204716394c4263bb976dfbb7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2209391Reviewed-by: Yusuf Ozuysal <yusufo@chromium.org>
Commit-Queue: Ganggui Tang <gogerald@chromium.org>
Auto-Submit: Ganggui Tang <gogerald@chromium.org>
Cr-Commit-Position: refs/heads/master@{#772431}

chrome/android/java/src/org/chromium/chrome/browser/toolbar/NewTabButton.java

@@ -18,6 +18,7 @@ import org.chromium.chrome.R;
 import org.chromium.chrome.browser.device.DeviceClassManager;
 import org.chromium.chrome.browser.tasks.tab_management.TabUiFeatureUtilities;
 import org.chromium.chrome.browser.toolbar.IncognitoStateProvider.IncognitoStateObserver;
+import org.chromium.chrome.features.start_surface.StartSurfaceConfiguration;
 import org.chromium.ui.base.DeviceFormFactor;
 import org.chromium.ui.widget.ChromeImageButton;
 import org.chromium.ui.widget.Toast;
@@ -86,7 +87,8 @@ public class NewTabButton
         final boolean shouldUseLightMode =
                 DeviceFormFactor.isNonMultiDisplayContextOnTablet(getContext())
                 || ((DeviceClassManager.enableAccessibilityLayout()
-                            || TabUiFeatureUtilities.isGridTabSwitcherEnabled())
+                            || TabUiFeatureUtilities.isGridTabSwitcherEnabled()
+                            || StartSurfaceConfiguration.isStartSurfaceEnabled())
                         && mIsIncognito);
         ApiCompatibilityUtils.setImageTintList(
                 this, shouldUseLightMode ? mLightModeTint : mDarkModeTint);