Use NewTabButton for new tab variation in GTS

Bug: 1042015
Change-Id: Ic1ad4c0902725bc0a096b72f05f5fab92ef9d4d0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2001265
Auto-Submit: Yue Zhang <yuezhanggg@chromium.org>
Reviewed-by: Theresa  <twellington@chromium.org>
Reviewed-by: Wei-Yin Chen (陳威尹) <wychen@chromium.org>
Commit-Queue: Yue Zhang <yuezhanggg@chromium.org>
Cr-Commit-Position: refs/heads/master@{#731803}

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

@@ -18,15 +18,13 @@
         android:background="?attr/selectableItemBackground"
         android:orientation="horizontal"
         android:visibility="gone">
-        <ImageView
-            android:layout_width="@dimen/toolbar_button_width"
-            android:layout_height="56dp"
+        <org.chromium.chrome.browser.toolbar.NewTabButton
+            style="@style/ToolbarButton"
+            android:layout_width="wrap_content"
             android:layout_gravity="start|top"
-            android:scaleType="center"
             android:paddingStart="16dp"
             android:paddingEnd="16dp"
-            app:srcCompat="@drawable/new_tab_icon"
-            android:contentDescription="@string/accessibility_toolbar_btn_new_tab"/>
+            android:contentDescription="@string/accessibility_toolbar_btn_new_tab" />
         <TextView
             android:layout_width="wrap_content"
             android:layout_height="match_parent"