Update dialog button text color for Harmony per the latest button spec

ui/views/style/typography_provider.cc

 // 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.
 
 #include "ui/views/style/typography_provider.h"
 
 #include "base/logging.h"
 #include "ui/base/default_style.h"
 #include "ui/base/resource/resource_bundle.h"
 #include "ui/native_theme/native_theme.h"
@@ skipping 34 matching lines @@
   Font::Weight font_weight;
   GetDefaultFont(context, style, &size_delta, &font_weight);
   return ResourceBundle::GetSharedInstance().GetFontListWithDelta(
       size_delta, Font::NORMAL, font_weight);
 }
 
 SkColor DefaultTypographyProvider::GetColor(
     int context,
     int style,
     const ui::NativeTheme& theme) const {
+  if (context == style::CONTEXT_BUTTON_MD) {
+    ui::NativeTheme::ColorId color_id =
+        ui::NativeTheme::kColorId_ButtonEnabledColor;
+    switch (style) {
+      case views::style::STYLE_DIALOG_BUTTON_DEFAULT:
+        color_id = ui::NativeTheme::kColorId_TextOnProminentButtonColor;
+        break;
+      case views::style::STYLE_DISABLED:
+        color_id = ui::NativeTheme::kColorId_ButtonDisabledColor;
+        break;
+    }
+    return theme.GetSystemColor(color_id);
+  }
+
   return theme.GetSystemColor(
       (style == style::STYLE_DISABLED)
           ? ui::NativeTheme::kColorId_LabelDisabledColor
           : ui::NativeTheme::kColorId_LabelEnabledColor);
 }
 
 int DefaultTypographyProvider::GetLineHeight(int context, int style) const {
   return 0;
 }
 
@@ skipping 30 matching lines @@
         *font_weight = GetValueBolderThan(
             ResourceBundle::GetSharedInstance()
                 .GetFontListWithDelta(*size_delta, Font::NORMAL, *font_weight)
                 .GetFontWeight());
       }
       break;
   }
 }
 
 }  // namespace views