Remove nav bar divider line when nav bar color is black

This effectively removes the grey navigation bar divider line when the
navigation bar color is black on Android P+.

BUG=844173

Change-Id: I5147f63aadd9d79d084fa582284e46fb2c6b6fe9
Reviewed-on: https://chromium-review.googlesource.com/1119369
Commit-Queue: Theresa <twellington@chromium.org>
Reviewed-by: Ted Choc <tedchoc@chromium.org>
Cr-Commit-Position: refs/heads/master@{#571335}

chrome/android/java/src/org/chromium/chrome/browser/NavigationBarColorController.java

@@ -4,6 +4,7 @@
 
 package org.chromium.chrome.browser;
 
+import android.annotation.SuppressLint;
 import android.annotation.TargetApi;
 import android.content.res.Resources;
 import android.graphics.Color;
@@ -139,9 +140,21 @@ public class NavigationBarColorController implements VrModeObserver {
                                   mResources, R.color.bottom_system_nav_color)
                         : Color.BLACK);
 
+        setNavigationBarColor(useLightNavigation);
+
         updateSystemUiVisibility(useLightNavigation);
     }
 
+    @SuppressLint("NewApi")
+    private void setNavigationBarColor(boolean useLightNavigation) {
+        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.P) {
+            mWindow.setNavigationBarDividerColor(useLightNavigation
+                            ? ApiCompatibilityUtils.getColor(
+                                      mResources, R.color.bottom_system_nav_divider_color)
+                            : Color.BLACK);
+        }
+    }
+
     private void updateSystemUiVisibility(boolean useLightNavigation) {
         int visibility = mRootView.getSystemUiVisibility();
         if (useLightNavigation) {