Start disabling GYP by default in runhooks in some configurations.

build/gyp_chromium.py

Index: build/gyp_chromium.py
diff --git a/build/gyp_chromium.py b/build/gyp_chromium.py
index 3c975d6a4683920e5eea67d86424523c86623539..e491216ef2d4bf198a693a4dde1a6920857447cb 100644
--- a/build/gyp_chromium.py
+++ b/build/gyp_chromium.py
@@ -320,6 +320,22 @@ def main():
   if mac_toolchain_dir:
     args.append('-Gmac_toolchain_dir=' + mac_toolchain_dir)
 
+  # TODO(crbug.com/432967) - We are eventually going to switch GYP off
+  # by default for all Chromium builds, so this list of configurations
+  # will get broader and broader.
+  running_as_hook = '--running-as-hook'
+  if (running_as_hook in args and
+      os.environ.get('GYP_CHROMIUM_NO_ACTION', None) != '0' and
+      (sys.platform.startswith('linux') and not gyp_vars_dict)):
+    print 'GYP is now disabled in this configuration by default in runhooks.\n'
+    print 'If you really want to run this, either run '
+    print '`python build/gyp_chromium.py` explicitly by hand'
+    print 'or set the environment variable GYP_CHROMIUM_NO_ACTION=0.'
+    sys.exit(0)
+
+  if running_as_hook in args:
+    args.remove(running_as_hook)
+
   if not use_analyzer:
     print 'Updating projects from gyp files...'
     sys.stdout.flush()