Initial switch to Chromium-style CHECK_* and DCHECK_* macros.

src/x64/assembler-x64.cc

Index: src/x64/assembler-x64.cc
diff --git a/src/x64/assembler-x64.cc b/src/x64/assembler-x64.cc
index 725dcdb5bde69e551ceecee460c4236118af405d..b3ba7c21b9b7214606652cf0f162e0c23643805c 100644
--- a/src/x64/assembler-x64.cc
+++ b/src/x64/assembler-x64.cc
@@ -57,7 +57,7 @@ bool OSHasAVXSupport() {
   // The buffer now contains a string of the form XX.YY.ZZ, where
   // XX is the major kernel version component.
   char* period_pos = strchr(buffer, '.');
-  DCHECK_NOT_NULL(period_pos);
+  DCHECK(period_pos);
   *period_pos = '\0';
   long kernel_version_major = strtol(buffer, nullptr, 10);  // NOLINT
   if (kernel_version_major <= 13) return false;