Fix sense of CheckOpResult comment.

base/logging.h

Index: base/logging.h
diff --git a/base/logging.h b/base/logging.h
index 2c8959c72c95aad8f3ec93a9e25e6bbe09e5d0cb..07674698e0220dbd7d2ab1662556e2853adc275d 100644
--- a/base/logging.h
+++ b/base/logging.h
@@ -430,7 +430,7 @@ const LogSeverity LOG_0 = LOG_ERROR;
 // 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_; }