Add installer::SetupSingleton.

chrome/installer/util/installer_state.h

Index: chrome/installer/util/installer_state.h
diff --git a/chrome/installer/util/installer_state.h b/chrome/installer/util/installer_state.h
index 600965ef5a94f98c476494823976d678867316d0..8179e3455c60e3174cfcdb974c53de0443d2c862 100644
--- a/chrome/installer/util/installer_state.h
+++ b/chrome/installer/util/installer_state.h
@@ -119,6 +119,11 @@ class InstallerState {
   // The full path to the place where the operand resides.
   const base::FilePath& target_path() const { return target_path_; }
 
+  // Sets the value returned by target_path().
+  void set_target_path_for_testing(const base::FilePath& target_path) {
+    target_path_ = target_path;
+  }
+
   // True if the "msi" preference is set or if a product with the "msi" state
   // flag is set is to be operated on.
   bool is_msi() const { return msi_; }