Make ChromeShell activity use AppCompat theme to match official Chrome.

BUG=None

Review URL: https://codereview.chromium.org/684453004

Cr-Commit-Position: refs/heads/master@{#301531}

chrome/android/shell/java/AndroidManifest.xml

@@ -43,7 +43,7 @@
             android:label="Chrome Shell">
         <activity android:name="org.chromium.chrome.shell.ChromeShellActivity"
                   android:launchMode="singleTask"
-                  android:theme="@android:style/Theme.Holo.Light.NoActionBar"
+                  android:theme="@style/MainTheme"
                   android:configChanges="orientation|keyboardHidden|keyboard|screenSize"
                   android:hardwareAccelerated="true">
               <intent-filter>

chrome/android/shell/res/drawable/progress.xml

@@ -8,6 +8,6 @@
 
 <clip xmlns:android="http://schemas.android.com/apk/res/android">
     <shape>
-        <solid android:color="@android:color/holo_blue_light" />
+        <solid android:color="@color/material_deep_teal_500" />
     </shape>
 </clip>

chrome/android/shell/res/values-v17/styles.xml

+<?xml version="1.0" encoding="utf-8"?>
+
+<!-- Copyright 2014 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.
+-->
+
+<resources>
+
+    <style name="MainTheme" parent="Theme.AppCompat.Light.NoActionBar">
+        <item name="android:windowContentOverlay">@null</item>
+        <item name="android:windowActionBar">false</item>
+        <item name="android:windowNoTitle">true</item>
+
+        <!-- colorPrimary is used for the default action bar background -->
+        <item name="colorPrimary">@color/material_deep_teal_200</item>
+
+        <!-- colorPrimaryDark is used for the status bar -->
+        <item name="colorPrimaryDark">@color/material_deep_teal_500</item>
+    </style>
+
+</resources>
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