The preprocessor expression defined(COMPILER_GCC) is used in code copied
from the Chromium project, but COMPILER_GCC is not defined by GCC itself,
but by the following expression in Chromium's build_config.h:
#if defined(__GNUC__)
#define COMPILER_GCC 1
#elif // ...
It must therefore be changed when copying the code out of the Chromium
code base.