I've defined a function inside DCHECK_IS_ON compile guard flags. The only use of the function is inside a DCHECK macro, so it should never cause linking problems because of undefined function. 

However, the following patch fails in the chromeos_x86 bot:

https://codereview.chromium.org/815833005/#ps320001

Here is the undefined function error shown by the mentioned bot:

 https://build.chromium.org/p/tryserver.chromium.linux/builders/chromeos_x86-generic_chromium_compile_only_ng/builds/151912/steps/compile%20%28with%20patch%29/logs/stdio