GN: Allow users to enable DCHECK on Release builds.

build/common.gypi

 # 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.
 
 # IMPORTANT:
 # Please don't directly include this file if you are building via gyp_chromium,
 # since gyp_chromium is automatically forcing its inclusion.
 {
   # Variables expected to be overriden on the GYP command line (-D) or by
   # ~/.gyp/include.gypi.
@@ skipping 300 matching lines @@
       # Set to 1 to not store any build metadata, e.g. ifdef out all __DATE__
       # and __TIME__. Set to 0 to reenable the use of these macros in the code
       # base. See http://crbug.com/314403.
       'dont_embed_build_metadata%': 1,
 
       # Set to 1 to force Visual C++ to use legacy debug information format /Z7.
       # This is useful for parallel compilation tools which can't support /Zi.
       # Only used on Windows.
       'win_z7%' : 0,
 
-      # Set to 1 to enable dcheck in release.
+      # Set to 1 to enable dcheck in Release build.
       'dcheck_always_on%': 0,
 
       # Set to 1 to make a build that disables unshipped tracing events.
       # Note: this setting is ignored if buildtype=="Official".
       'tracing_like_official_build%': 0,
 
       # Disable image loader component extension by default.
       'image_loader_extension%': 0,
 
       # Set NEON compilation flags.
@@ skipping 5559 matching lines @@
     # settings in target dicts.  SYMROOT is a special case, because many other
     # Xcode variables depend on it, including variables such as
     # PROJECT_DERIVED_FILE_DIR.  When a source group corresponding to something
     # like PROJECT_DERIVED_FILE_DIR is added to a project, in order for the
     # files to appear (when present) in the UI as actual files and not red
     # red "missing file" proxies, the correct path to PROJECT_DERIVED_FILE_DIR,
     # and therefore SYMROOT, needs to be set at the project level.
     'SYMROOT': '<(DEPTH)/xcodebuild',
   },
 }