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

content/public/common/manifest.cc

Index: content/public/common/manifest.cc
diff --git a/content/public/common/manifest.cc b/content/public/common/manifest.cc
index 8e09aad2e71ea9aa86f681d7df267f2dbbddb09c..e0c9cfc4fd1cc92fa3d5df51065d16449110c941 100644
--- a/content/public/common/manifest.cc
+++ b/content/public/common/manifest.cc
@@ -6,12 +6,6 @@
 
 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() { }
@@ -34,9 +28,7 @@ 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;
@@ -53,8 +45,8 @@ bool Manifest::IsEmpty() const {
          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();
 }