Force migrate all clients from multi-install back to single-install.

chrome/installer/mini_installer/configuration.h

Index: chrome/installer/mini_installer/configuration.h
diff --git a/chrome/installer/mini_installer/configuration.h b/chrome/installer/mini_installer/configuration.h
index d35127acc2524305a991e0d44502ab0584af108f..006fc2ccc78cd6100356311de120ead6cc19532c 100644
--- a/chrome/installer/mini_installer/configuration.h
+++ b/chrome/installer/mini_installer/configuration.h
@@ -40,23 +40,21 @@ class Configuration {
   // Returns the original command line.
   const wchar_t* command_line() const { return command_line_; }
 
-  // Returns the app guid to be used for Chrome.  --chrome-sxs on the command
-  // line makes this the canary's app guid.
+  // Returns the app guid to be used for Chrome. --chrome-sxs on the command
+  // line makes this the canary's app guid (Google Chrome only).
   const wchar_t* chrome_app_guid() const { return chrome_app_guid_; }
 
-  // Returns true if --chrome is explicitly or implicitly on the command line.
-  bool has_chrome() const { return has_chrome_; }
-
-  // Returns true if --multi-install is on the command line.
-  bool is_multi_install() const { return is_multi_install_; }
-
   // Returns true if --system-level is on the command line or if
   // GoogleUpdateIsMachine=1 is set in the process's environment.
   bool is_system_level() const { return is_system_level_; }
 
-  // Retuns true if --chrome-sxs is on the command line.
+  // Retuns true if --chrome-sxs is on the command line (Google Chrome only).

[gab, 2016/12/12 21:38:16]

Why make this Google Chrome only? Chromium SxS exists, no?

[grt (UTC plus 2), 2016/12/13 09:20:37]

Nope:
https://cs.chromium.org/chromium/src/chrome/installer/util/browser_distributi...

[gab, 2016/12/14 16:33:38]

I see, thought it did because we have test_installer configs for SxS but just
realized they're all behind $SUPPORTS_SXS (which I can't figure out where we
ever set to True..?!).

[grt (UTC plus 2), 2016/12/14 20:38:45]

It's magic!

(well, not really, but it isn't obvious when searching for it:
https://cs.chromium.org/chromium/src/chrome/test/mini_installer/variable_expa...
)

   bool is_side_by_side() const { return is_side_by_side_; }
 
+  // Returns true if an existing multi-install Chrome is being updated (Google
+  // Chrome only).
+  bool is_updating_multi_chrome() const { return is_updating_multi_chrome_; }
+
   // Returns true if any invalid switch is found on the command line.
   bool has_invalid_switch() const { return has_invalid_switch_; }
 
@@ -73,26 +71,31 @@ class Configuration {
   const wchar_t* command_line_;
   int argument_count_;
   Operation operation_;
-  bool has_chrome_;
-  bool is_multi_install_;
   bool is_system_level_;
   bool is_side_by_side_;
+  bool is_updating_multi_chrome_;
   bool has_invalid_switch_;
   const wchar_t* previous_version_;
 
  protected:
   typedef StackString<128> ValueString;
+  enum class RegistryLocation {
+    CLIENTS_KEY,
+    CLIENT_STATE_KEY,
+  };
 
   // Virtual for testing.
-  virtual bool ReadClientStateRegistryValue(
-      const HKEY root_key, const wchar_t* app_guid,
-      LONG* retval, ValueString& value);
+  virtual LONG ReadRegistryValue(RegistryLocation location,
+                                 const wchar_t* app_guid,
+                                 const wchar_t* value_name,
+                                 ValueString* value) const;
 
  private:
   Configuration(const Configuration&);
   Configuration& operator=(const Configuration&);
 
-  void SetChromeAppGuid();
+  // Returns true if multi-install Chrome is already present on the machine.
+  bool IsUpdatingMultiChrome() const;
 };
 
 }  // namespace mini_installer