Fix sense of CheckOpResult comment.

base/logging.h

 // Copyright (c) 2012 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.
 
 #ifndef BASE_LOGGING_H_
 #define BASE_LOGGING_H_
 
 #include <stddef.h>
 
 #include <cassert>
@@ skipping 412 matching lines @@
   LAZY_STREAM(PLOG_STREAM(severity), LOG_IS_ON(severity) && (condition))
 
 // The actual stream used isn't important.
 #define EAT_STREAM_PARAMETERS                                           \
   true ? (void) 0 : ::logging::LogMessageVoidify() & LOG_STREAM(FATAL)
 
 // Captures the result of a CHECK_EQ (for example) and facilitates testing as a
 // boolean.
 class CheckOpResult {
  public:
-  // |message| must be non-null iff the check failed.
+  // |message| must be non-null if and only if the check failed.
   CheckOpResult(std::string* message) : message_(message) {}
   // Returns true if the check succeeded.
   operator bool() const { return !message_; }
   // Returns the message.
   std::string* message() { return message_; }
 
  private:
   std::string* message_;
 };
 
@@ skipping 512 matching lines @@
 #elif NOTIMPLEMENTED_POLICY == 5
 #define NOTIMPLEMENTED() do {\
   static bool logged_once = false;\
   LOG_IF(ERROR, !logged_once) << NOTIMPLEMENTED_MSG;\
   logged_once = true;\
 } while(0);\
 EAT_STREAM_PARAMETERS
 #endif
 
 #endif  // BASE_LOGGING_H_