Add divider line to bottom system nav

BUG=805976

Change-Id: I7c3a973b52c512fef38398e3bc98c1e9c848ebe4
Reviewed-on: https://chromium-review.googlesource.com/887563
Commit-Queue: Theresa <twellington@chromium.org>
Reviewed-by: Ted Choc <tedchoc@chromium.org>
Cr-Commit-Position: refs/heads/master@{#532024}

chrome/android/java/res/values-v27/styles.xml

@@ -6,18 +6,22 @@
 <resources xmlns:tools="http://schemas.android.com/tools">
     <style name="MainTheme" parent="MainThemeBase">
         <item name="android:navigationBarColor">@color/bottom_system_nav_color</item>
+        <item name="android:navigationBarDividerColor">@color/bottom_system_nav_divider_color</item>
         <item name="android:windowLightNavigationBar">true</item>
     </style>
     <style name="FullscreenWhite" parent="FullscreenWhiteBase">
         <item name="android:navigationBarColor">@color/bottom_system_nav_color</item>
+        <item name="android:navigationBarDividerColor">@color/bottom_system_nav_divider_color</item>
         <item name="android:windowLightNavigationBar">true</item>
     </style>
     <style name="ThemeWithActionBar" parent="ThemeWithActionBarBase">
         <item name="android:navigationBarColor">@color/bottom_system_nav_color</item>
+        <item name="android:navigationBarDividerColor">@color/bottom_system_nav_divider_color</item>
         <item name="android:windowLightNavigationBar">true</item>
     </style>
     <style name="DialogWhenLarge" parent="DialogWhenLargeBase">
         <item name="android:navigationBarColor">@color/bottom_system_nav_color</item>
+        <item name="android:navigationBarDividerColor">@color/bottom_system_nav_divider_color</item>
         <item name="android:windowLightNavigationBar">true</item>
     </style>
 </resources>

chrome/android/java/res/values/colors.xml

@@ -27,6 +27,7 @@
     <color name="google_grey_600">#757575</color>
     <color name="grey_alpha_90">#E6505050</color>
     <color name="black_alpha_11">#1D000000</color>
+    <color name="black_alpha_12">#1F000000</color>
     <color name="white_alpha_50">#80FFFFFF</color>
     <color name="white_alpha_54">#8AFFFFFF</color>
     <color name="black_alpha_65">#A6000000</color>
@@ -209,5 +210,6 @@
     <color name="google_blue_500_alpha_38_opaque">#B7D1FB</color>
     <color name="toolbar_shadow_color">@color/black_alpha_11</color>
     <color name="bottom_system_nav_color">@android:color/white</color>
+    <color name="bottom_system_nav_divider_color">@color/black_alpha_12</color>
 
 </resources>