[WIP] Use Optional<SkColor> instead of int64 for colors in Manifest.

content/public/common/manifest.cc

 // 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.
 
 #include "content/public/common/manifest.h"
 
 namespace content {
 
-// We need to provide a value here which is out of the range of a 32-bit integer
-// since otherwise we would not be able to check whether a theme color was valid
-// or not. The simplest way to do this is to simply add one to the maximum
-// possible 32-bit integer.
-const int64_t Manifest::kInvalidOrMissingColor =
-    static_cast<int64_t>(std::numeric_limits<int32_t>::max()) + 1;
 const size_t Manifest::kMaxIPCStringLength = 4 * 1024;
 
 Manifest::Icon::Icon() { }
 
 Manifest::Icon::Icon(const Icon& other) = default;
 
 Manifest::Icon::~Icon() {
 }
 
 bool Manifest::Icon::operator==(const Manifest::Icon& other) const {
   return src == other.src && type == other.type && sizes == other.sizes;
 }
 
 Manifest::RelatedApplication::RelatedApplication() {
 }
 
 Manifest::RelatedApplication::~RelatedApplication() {
 }
 
 Manifest::Manifest()
     : display(blink::WebDisplayModeUndefined),
       orientation(blink::WebScreenOrientationLockDefault),
-      prefer_related_applications(false),
-      theme_color(Manifest::kInvalidOrMissingColor),
-      background_color(Manifest::kInvalidOrMissingColor) {
+      prefer_related_applications(false) {
 }
 
 Manifest::Manifest(const Manifest& other) = default;
 
 Manifest::~Manifest() {
 }
 
 bool Manifest::IsEmpty() const {
   return name.is_null() &&
          short_name.is_null() &&
          start_url.is_empty() &&
          display == blink::WebDisplayModeUndefined &&
          orientation == blink::WebScreenOrientationLockDefault &&
          icons.empty() &&
          related_applications.empty() &&
          !prefer_related_applications &&
-         theme_color == Manifest::kInvalidOrMissingColor &&
-         background_color == Manifest::kInvalidOrMissingColor &&
+         !theme_color.has_value() &&
+         !background_color.has_value() &&
          gcm_sender_id.is_null() &&
          scope.is_empty();
 }
 
 } // namespace content