Use the single char overload of append() when possible.

third_party/WebKit/Source/platform/weborigin/SecurityOrigin.cpp

 /*
  * Copyright (C) 2007 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
  * 2.  Redistributions in binary form must reproduce the above copyright
@@ skipping 487 matching lines @@
     buildRawString(result, true);
     return result.toAtomicString();
 }
 
 void SecurityOrigin::buildRawString(StringBuilder& builder, bool includeSuborigin) const
 {
     builder.append(m_protocol);
     builder.append("://");
     if (includeSuborigin && hasSuborigin()) {
         builder.append(m_suborigin.name());
-        builder.append("_");
+        builder.append('_');
     }
     builder.append(m_host);
 
     if (m_port) {
         builder.append(':');
         builder.appendNumber(m_port);
     }
 }
 
 PassRefPtr<SecurityOrigin> SecurityOrigin::createFromString(const String& originString)
@@ skipping 62 matching lines @@
     m_blockLocalAccessFromLocalOrigin = privilegeData->m_blockLocalAccessFromLocalOrigin;
 }
 
 void SecurityOrigin::setUniqueOriginIsPotentiallyTrustworthy(bool isUniqueOriginPotentiallyTrustworthy)
 {
     ASSERT(!isUniqueOriginPotentiallyTrustworthy || isUnique());
     m_isUniqueOriginPotentiallyTrustworthy = isUniqueOriginPotentiallyTrustworthy;
 }
 
 } // namespace blink