content: make theme_color more resilient to casting issues

content/renderer/manifest/manifest_parser.cc

Index: content/renderer/manifest/manifest_parser.cc
diff --git a/content/renderer/manifest/manifest_parser.cc b/content/renderer/manifest/manifest_parser.cc
index 6b021d2a7a30286f1cbd292e161a3c5e5f495f71..9ce89107f28011091e1e21487f685e0ac4065294 100644
--- a/content/renderer/manifest/manifest_parser.cc
+++ b/content/renderer/manifest/manifest_parser.cc
@@ -427,7 +427,11 @@ int64_t ManifestParser::ParseThemeColor(
       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(