[Dark] Update reader mode CCT color scheme to match dark mode state

Bug: 958986
Change-Id: I276bc5a6afd806e9814be6a3031db80f2c11a459
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1600639Reviewed-by: Matthew Jones <mdjones@chromium.org>
Commit-Queue: Becky Zhou <huayinz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#657734}

chrome/android/java/src/org/chromium/chrome/browser/dom_distiller/ReaderModeManager.java

@@ -499,6 +499,9 @@ public class ReaderModeManager extends TabModelSelectorTabObserver {
 
         CustomTabsIntent.Builder builder = new CustomTabsIntent.Builder();
         builder.setShowTitle(true);
+        builder.setColorScheme(mChromeActivity.getNightModeStateProvider().isInNightMode()
+                        ? CustomTabsIntent.COLOR_SCHEME_DARK
+                        : CustomTabsIntent.COLOR_SCHEME_LIGHT);
         CustomTabsIntent customTabsIntent = builder.build();
         customTabsIntent.intent.setClassName(mChromeActivity, CustomTabActivity.class.getName());