Delete unused code in chrome/common or mark them as platform specific.

chrome/installer/util/util_constants.cc

Index: chrome/installer/util/util_constants.cc
diff --git a/chrome/installer/util/util_constants.cc b/chrome/installer/util/util_constants.cc
index 697526225c09495187205f510bf961455af31957..bfb54066eac4e7faa4adb61aefcbca47eeef7825 100644
--- a/chrome/installer/util/util_constants.cc
+++ b/chrome/installer/util/util_constants.cc
@@ -186,6 +186,15 @@ const char kOutputFile[] = "output-file";
 
 }  // namespace switches
 
+namespace env_vars {
+
+// The presence of this environment variable with a value of 1 implies that
+// setup.exe should run as a system installation regardless of what is on the
+// command line.
+const char kGoogleUpdateIsMachineEnvVar[] = "GoogleUpdateIsMachine";
+
+}  // namespace env_vars
+
 // The Active Setup executable will be an identical copy of setup.exe; this is
 // necessary because Windows' installer detection heuristics (which include
 // things like process name being "setup.exe") will otherwise force elevation