Material Design: Fix MdLabelButton not updating text colors on theme changes

ui/views/controls/button/md_text_button.cc

 // Copyright 2015 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/controls/button/md_text_button.h"
 
 #include "base/i18n/case_conversion.h"
 #include "base/memory/ptr_util.h"
 #include "ui/base/material_design/material_design_controller.h"
 #include "ui/gfx/canvas.h"
@@ skipping 233 matching lines @@
   SetBorder(CreateEmptyBorder(top_padding, kHorizontalPadding, bottom_padding,
                               kHorizontalPadding));
 }
 
 void MdTextButton::UpdateColors() {
   ui::NativeTheme::ColorId fg_color_id =
       is_prominent_ ? ui::NativeTheme::kColorId_TextOnProminentButtonColor
                     : ui::NativeTheme::kColorId_ButtonEnabledColor;
 
   ui::NativeTheme* theme = GetNativeTheme();
-  if (!explicitly_set_normal_color())
+  if (!explicitly_set_normal_color()) {
+    const auto colors = explicitly_set_colors();
     LabelButton::SetEnabledTextColors(theme->GetSystemColor(fg_color_id));
+    set_explicitly_set_colors(colors);
+  }
 
   // Prominent buttons keep their enabled text color; disabled state is conveyed
   // by shading the background instead.
   if (is_prominent_)
     SetTextColor(STATE_DISABLED, theme->GetSystemColor(fg_color_id));
 
   SkColor text_color = label()->enabled_color();
   SkColor bg_color =
       theme->GetSystemColor(ui::NativeTheme::kColorId_DialogBackground);
 
@@ skipping 28 matching lines @@
         stroke_color, gfx::kDisabledControlAlpha);
   }
 
   DCHECK_EQ(SK_AlphaOPAQUE, static_cast<int>(SkColorGetA(bg_color)));
   set_background(Background::CreateBackgroundPainter(
       true, Painter::CreateRoundRectWith1PxBorderPainter(
                 bg_color, stroke_color, kInkDropSmallCornerRadius)));
 }
 
 }  // namespace views