Let DCHECK in non-official-release build be opt-in with dcheck_always_on=1 only

base/base_switches.h

Index: base/base_switches.h
diff --git a/base/base_switches.h b/base/base_switches.h
index b679e6d9ebf1a7f4c79dfb831e1c1bab3dd71d33..70d02e20ee107bf9fe2c63172b21d3d9e4daf6e2 100644
--- a/base/base_switches.h
+++ b/base/base_switches.h
@@ -14,7 +14,6 @@ namespace switches {
 extern const char kDebugOnStart[];
 extern const char kDisableBreakpad[];
 extern const char kEnableCrashReporter[];
-extern const char kEnableDCHECK[];
 extern const char kFullMemoryCrashReport[];
 extern const char kNoErrorDialogs[];
 extern const char kProfilerTiming[];