content: make theme_color more resilient to casting issues

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 {
 
 const double Manifest::Icon::kDefaultDensity = 1;
-const int64_t Manifest::kInvalidOrMissingThemeColor = -1;
+const int64_t Manifest::kInvalidOrMissingThemeColor =
+    static_cast<int64_t>(std::numeric_limits<int32_t>::max()) + 1;
 const size_t Manifest::kMaxIPCStringLength = 4 * 1024;
 
 Manifest::Icon::Icon()
     : density(kDefaultDensity) {
 }
 
 Manifest::Icon::~Icon() {
 }
 
 Manifest::RelatedApplication::RelatedApplication() {
@@ skipping 19 matching lines @@
          display == DISPLAY_MODE_UNSPECIFIED &&
          orientation == blink::WebScreenOrientationLockDefault &&
          icons.empty() &&
          related_applications.empty() &&
          !prefer_related_applications &&
          theme_color == Manifest::kInvalidOrMissingThemeColor &&
          gcm_sender_id.is_null();
 }
 
 } // namespace content