Make showing the page title in a custom tab a dev option

chrome/android/java/res/layout/custom_tabs_toolbar.xml

 <?xml version="1.0" encoding="utf-8"?>
 <!-- Copyright 2015 The Chromium Authors. All rights reserved.
      Use of this source code is governed by a BSD-style license that can be
      found in the LICENSE file. -->
 
 <org.chromium.chrome.browser.toolbar.CustomTabToolbar xmlns:android="http://schemas.android.com/apk/res/android">
     <org.chromium.chrome.browser.widget.TintedImageButton
         android:id="@+id/back_button"
         style="@style/ToolbarButton"
         android:layout_gravity="center_vertical"
@@ skipping 17 matching lines @@
         <TextView
             android:id="@+id/title_bar"
             android:background="@null"
             android:layout_width="wrap_content"
             android:layout_height="wrap_content"
             android:layout_marginBottom="16dp"
             android:layout_gravity="top"
             android:maxLines="1"
             android:paddingEnd="@dimen/toolbar_edge_padding"
             android:textSize="@dimen/custom_tabs_title_text_size"
-            android:inputType="none" />
+            android:inputType="none"
+            android:visibility="gone" />
         <org.chromium.chrome.browser.omnibox.UrlBar
             android:id="@+id/url_bar"
             android:background="@null"
             android:layout_width="wrap_content"
             android:layout_height="wrap_content"
             android:layout_gravity ="bottom"
             android:maxLines="1"
             android:paddingEnd="@dimen/toolbar_edge_padding"
-            android:textSize="@dimen/custom_tabs_url_text_size"
+            android:textSize="@dimen/location_bar_url_text_size"
             android:inputType="none" />
     </FrameLayout>
     <ImageButton
         android:id="@+id/action_button"
         style="@style/ToolbarButton"
         android:layout_width="wrap_content"
         android:maxWidth="@dimen/custom_tabs_toolbar_maxWidth"
         android:paddingTop="@dimen/custom_tabs_toolbar_vertical_padding"
         android:paddingBottom="@dimen/custom_tabs_toolbar_vertical_padding"
         android:adjustViewBounds="true"
@@ skipping 12 matching lines @@
         android:contentDescription="@string/accessibility_toolbar_btn_menu"
         android:background="@null" />
     <org.chromium.chrome.browser.widget.ToolbarProgressBar
         android:id="@+id/progress"
         style="@style/Widget.AppCompat.ProgressBar.Horizontal"
         android:progressDrawable="@drawable/progress_bar"
         android:layout_width="match_parent"
         android:layout_height="2dp"
         android:progress="0" />
 </org.chromium.chrome.browser.toolbar.CustomTabToolbar>