[Snowflake] Fix modal dialog wrong button colors

Use AppCompatButton in modal_dialog_view so that the text appearance
can be applied to pre L devices.

Bug: 872212
Change-Id: Ib84be209d086306983267cff5be0151202093ad6
Reviewed-on: https://chromium-review.googlesource.com/1173450
Commit-Queue: Becky Zhou <huayinz@chromium.org>
Reviewed-by: Theresa <twellington@chromium.org>
Cr-Commit-Position: refs/heads/master@{#583337}

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

@@ -58,13 +58,13 @@
         android:layout_height="wrap_content"
         style="?attr/buttonBarStyle">
 
-        <Button
+        <android.support.v7.widget.AppCompatButton
             android:id="@+id/negative_button"
             android:layout_width="wrap_content"
             android:layout_height="wrap_content"
             style="?attr/buttonBarNegativeButtonStyle" />
 
-        <Button
+        <android.support.v7.widget.AppCompatButton
             android:id="@+id/positive_button"
             android:layout_width="wrap_content"
             android:layout_height="wrap_content"

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

@@ -138,13 +138,8 @@
         <item name="android:paddingBottom">@dimen/modal_dialog_control_padding_vertical</item>
     </style>
 
-    <!-- TODO(huayinz): Move this to pre-defined style once we have the disabled state defined  -->
-    <style name="TextAppearance.ModalDialogButton" parent="BlueButtonText2">
-        <item name="android:textColor">@color/blue_when_enabled</item>
-    </style>
-
     <style name="ModalDialogButtonStyle" parent="Widget.AppCompat.Button.ButtonBar.AlertDialog">
-        <item name="android:textAppearance">@style/TextAppearance.ModalDialogButton</item>
+        <item name="android:textAppearance">@style/BlueButtonText2</item>
     </style>
 
     <style name="SimpleDialog" parent="AlertDialogTheme">