Use vectorized icon for default extensions icons

ui/native_theme/native_theme.h

 // Copyright (c) 2012 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.
 
 #ifndef UI_NATIVE_THEME_NATIVE_THEME_H_
 #define UI_NATIVE_THEME_NATIVE_THEME_H_
 
 #include "base/observer_list.h"
 #include "third_party/skia/include/core/SkColor.h"
 #include "ui/gfx/native_widget_types.h"
@@ skipping 306 matching lines @@
     // Positive text refers to good (often rendered in green) text, such as the
     // stock value went up.
     kColorId_ResultsTablePositiveText,
     kColorId_ResultsTablePositiveHoveredText,
     kColorId_ResultsTablePositiveSelectedText,
     // Negative text refers to something alarming (often rendered in red), such
     // as the stock value went down.
     kColorId_ResultsTableNegativeText,
     kColorId_ResultsTableNegativeHoveredText,
     kColorId_ResultsTableNegativeSelectedText,
+    // For MD icons.
+    kColorId_ChromeIconGrey,
     // Colors for the material spinner (aka throbber).
     kColorId_ThrobberSpinningColor,
     kColorId_ThrobberWaitingColor,
     kColorId_ThrobberLightColor,
     // TODO(benrg): move other hardcoded colors here.
 
     kColorId_NumColors,
   };
 
   // Return a color from the system theme.
@@ skipping 24 matching lines @@
  private:
   // Observers to notify when the native theme changes.
   base::ObserverList<NativeThemeObserver> native_theme_observers_;
 
   DISALLOW_COPY_AND_ASSIGN(NativeTheme);
 };
 
 }  // namespace ui
 
 #endif  // UI_NATIVE_THEME_NATIVE_THEME_H_