content: make theme_color more resilient to casting issues

content/renderer/manifest/manifest_parser.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/renderer/manifest/manifest_parser.h"
 
 #include "base/json/json_reader.h"
 #include "base/strings/nullable_string16.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/string_split.h"
@@ skipping 409 matching lines @@
 
   blink::WebColor color;
   if (!blink::WebCSSParser::parseColor(&color, theme_color.string())) {
       errors_.push_back(GetErrorPrefix() +
                         "property 'theme_color' ignored, '" +
                         base::UTF16ToUTF8(theme_color.string()) +
                         "' is not a valid color.");
       return Manifest::kInvalidOrMissingThemeColor;
   }
 
-  return static_cast<int64_t>(color);
+  // We do this here because Java does not have an unsigned int32 type so colors
+  // with high alpha values will be negative. Instead of doing the conversion
+  // after we pass over to Java, we do it here as it is easier and clearer.
+  int32_t signed_color = reinterpret_cast<int32_t&>(color);
+  return static_cast<int64_t>(signed_color);
 }
 
 base::NullableString16 ManifestParser::ParseGCMSenderID(
     const base::DictionaryValue& dictionary)  {
   return ParseString(dictionary, "gcm_sender_id", Trim);
 }
 
 } // namespace content