Wrap the conditional in CHECK with UNLIKELY since it is.

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>
 #include <cstring>
 #include <sstream>
 #include <string>
 #include <type_traits>
 #include <utility>
 
 #include "base/base_export.h"
+#include "base/compiler_specific.h"
 #include "base/debug/debugger.h"
 #include "base/macros.h"
 #include "base/template_util.h"
 #include "build/build_config.h"
 
 //
 // Optional message capabilities
 // -----------------------------
 // Assertion failed messages and fatal errors are displayed in a dialog box
 // before the application exits. However, running this UI creates a message
@@ skipping 447 matching lines @@
 
 #if defined(OFFICIAL_BUILD) && defined(NDEBUG)
 
 // Make all CHECK functions discard their log strings to reduce code bloat, and
 // improve performance, for official release builds.
 //
 // This is not calling BreakDebugger since this is called frequently, and
 // calling an out-of-line function instead of a noreturn inline macro prevents
 // compiler optimizations.
 #define CHECK(condition) \
-  !(condition) ? IMMEDIATE_CRASH() : EAT_STREAM_PARAMETERS
+  UNLIKELY(!(condition)) ? IMMEDIATE_CRASH() : EAT_STREAM_PARAMETERS
 
 #define PCHECK(condition) CHECK(condition)
 
 #define CHECK_OP(name, op, val1, val2) CHECK((val1) op (val2))
 
 #else  // !(OFFICIAL_BUILD && NDEBUG)
 
 #if defined(_PREFAST_) && defined(OS_WIN)
 // Use __analysis_assume to tell the VC++ static analysis engine that
 // assert conditions are true, to suppress warnings.  The LAZY_STREAM
@@ skipping 521 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_