added scale animation for context menu

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

Index: chrome/android/java/res/layout/tabular_context_menu.xml
diff --git a/chrome/android/java/res/layout/tabular_context_menu.xml b/chrome/android/java/res/layout/tabular_context_menu.xml
index 11998c6ed39020b97d1cfc6545f41ae002ae768d..c599696dba04b1c719f2c547c6ccb6b3b2fc3590 100644
--- a/chrome/android/java/res/layout/tabular_context_menu.xml
+++ b/chrome/android/java/res/layout/tabular_context_menu.xml
@@ -2,23 +2,34 @@
 <!-- Copyright 2017 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.contextmenu.TabularContextMenuViewPager
+<FrameLayout
     xmlns:android="http://schemas.android.com/apk/res/android"
     xmlns:app="http://schemas.android.com/apk/res-auto"
-    android:id="@+id/custom_pager"
-    android:layout_width="wrap_content"
-    android:layout_height="wrap_content"
-    android:layout_marginTop="20dp"
-    android:layout_marginBottom="20dp"
-    android:minWidth="280dp">
-    <android.support.design.widget.TabLayout
-        android:id="@+id/tab_layout"
+    android:id="@+id/context_menu_frame_layout"
+    android:background="@color/modal_dialog_scrim_color" >
+
+    <org.chromium.chrome.browser.contextmenu.TabularContextMenuViewPager
+        android:id="@+id/custom_pager"
+        android:background="@drawable/white_with_rounded_corners"
         android:layout_width="match_parent"
         android:layout_height="wrap_content"
-        android:background="@color/google_grey_100"
-        app:tabTextColor="#80000000"
-        app:tabSelectedTextColor="@color/light_active_color"
-        app:tabIndicatorColor="@color/light_active_color"
-        app:tabGravity="fill"
-        app:tabMode="fixed" />
-</org.chromium.chrome.browser.contextmenu.TabularContextMenuViewPager>
+        android:layout_marginTop="20dp"
+        android:layout_marginBottom="20dp"
+        android:minWidth="280dp"
+        android:layout_gravity="center">
+
+        <!-- tabMaxWidth is required otherwise tabGravity will have no effect when the context menu 
+             gets too large. -->
+        <android.support.design.widget.TabLayout
+            android:id="@+id/tab_layout"
+            android:layout_width="wrap_content"
+            android:layout_height="wrap_content"
+            android:background="@color/google_grey_100"
+            app:tabTextColor="@color/black_alpha_54"
+            app:tabSelectedTextColor="@color/light_active_color"
+            app:tabIndicatorColor="@color/light_active_color"
+            app:tabGravity="fill"
+            app:tabMode="fixed"
+            app:tabMaxWidth="2000dp" />
+    </org.chromium.chrome.browser.contextmenu.TabularContextMenuViewPager>
+</FrameLayout>