Fix sense of CheckOpResult comment.

base/logging.h

Index: base/logging.h
diff --git a/base/logging.h b/base/logging.h
index adf8fde620e4ddd8eb87b5453f6afca8f83f58fa..2c8959c72c95aad8f3ec93a9e25e6bbe09e5d0cb 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 null if and only if the check failed.
+  // |message| must be non-null iff the check failed.

[Nico, 2016/03/18 21:56:48]

Let's please not say "iff" in chromium code. "if and only if" says the same
thing without being heinous. We don't say this so often that we need to shorten
it to three letters.

[Wez, 2016/03/18 23:19:27]

I think it's a bit much to describe the standard shorthand for "if and only if"
as "heinous"... Nonetheless, expanded back out to more bodacious wording. ;)

   CheckOpResult(std::string* message) : message_(message) {}
   // Returns true if the check succeeded.
   operator bool() const { return !message_; }