Support migrating multi-install Chrome to single-install.

chrome/installer/setup/install_worker.cc

 // 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.
 //
 // This file contains the definitions of the installer functions that build
 // the WorkItemList used to install the application.
 
 #include "chrome/installer/setup/install_worker.h"
 
 #include <oaidl.h>
@@ skipping 1074 matching lines @@
       }
       install_list->AddDeleteRegValueWorkItem(
           root_key,
           dist->GetStateKey(),
           KEY_WOW64_32KEY,
           google_update::kRegUsageStatsField);
     }
   }
 }
 
+// Migrates the usagestats value from the binaries to Chrome when migrating
+// multi-install Chrome to single-install.
+void AddMigrateUsageStatesWorkItems(const InstallationState& original_state,
+                                    const InstallerState& installer_state,
+                                    WorkItemList* install_list) {
+  // Ensure that a non-multi install or update is being processed (i.e.,
+  // no "--multi-install" on the command line).
+  if (installer_state.is_multi_install())
+    return;
+
+  // Ensure that Chrome is the product being installed or updated (there are no
+  // other products, so it is especially unexpected for this to fail).
+  const Product* chrome_product =
+      installer_state.FindProduct(BrowserDistribution::CHROME_BROWSER);
+  if (!chrome_product) {
+    NOTREACHED();

[robertshield, 2015/01/28 23:17:59]

Is it worth logging this (and maybe other, but mostly this) failure in this
function to the installer log to help with debugging in the case of user error
reports?

[grt (UTC plus 2), 2015/01/29 17:56:51]

Excellent idea. Done.

+    return;
+  }
+
+  const ProductState* chrome_state = original_state.GetProductState(
+      installer_state.system_install(),
+      BrowserDistribution::CHROME_BROWSER);
+  // Bail out if there is not an existing multi-install Chrome that is being
+  // updated.
+  if (!chrome_state || !chrome_state->is_multi_install())
+    return;
+
+  const ProductState* binaries_state = original_state.GetProductState(
+      installer_state.system_install(),
+      BrowserDistribution::CHROME_BINARIES);
+
+  // There is nothing to be done if the binaries do not have stats.
+  DWORD usagestats = 0;
+  if (!binaries_state || !binaries_state->GetUsageStats(&usagestats))
+    return;
+
+  // Write the value that was read to Chrome's ClientState key.
+  install_list->AddSetRegValueWorkItem(
+      installer_state.root_key(),
+      chrome_product->distribution()->GetStateKey(),
+      KEY_WOW64_32KEY,
+      google_update::kRegUsageStatsField,
+      usagestats,
+      true);
+}
+
 bool AppendPostInstallTasks(const InstallerState& installer_state,
                             const base::FilePath& setup_path,
                             const Version* current_version,
                             const Version& new_version,
                             const base::FilePath& temp_path,
                             WorkItemList* post_install_task_list) {
   DCHECK(post_install_task_list);
 
   HKEY root = installer_state.root_key();
   const Products& products = installer_state.products();
@@ skipping 198 matching lines @@
                            add_language_identifier,
                            install_list);
 
     AddDelegateExecuteWorkItems(installer_state, target_path, new_version,
                                 product, install_list);
 
     AddActiveSetupWorkItems(installer_state, setup_path, new_version, product,
                             install_list);
   }
 
+  // Ensure that the Clients key for the binaries is gone for single installs.
+  if (!installer_state.is_multi_install()) {
+    BrowserDistribution* binaries_dist =
+        BrowserDistribution::GetSpecificDistribution(
+            BrowserDistribution::CHROME_BINARIES);
+    install_list->AddDeleteRegKeyWorkItem(root,
+                                          binaries_dist->GetVersionKey(),
+                                          KEY_WOW64_32KEY);
+  }
+
   // TODO(huangs): Implement actual migration code and remove the hack below.
   // If installing Chrome without the legacy stand-alone App Launcher (to be
   // handled later), add "shadow" App Launcher registry keys so Google Update
   // would recognize the "dr" value in the App Launcher ClientState key.
   // Checking .is_multi_install() excludes Chrome Canary and stand-alone Chrome.
   if (installer_state.is_multi_install() &&
       installer_state.FindProduct(BrowserDistribution::CHROME_BROWSER) &&
       !installer_state.FindProduct(BrowserDistribution::CHROME_APP_HOST)) {
     BrowserDistribution* shadow_app_launcher_dist =
         BrowserDistribution::GetSpecificDistribution(
@@ skipping 11 matching lines @@
   AddProductSpecificWorkItems(original_state,
                               installer_state,
                               setup_path,
                               new_version,
                               current_version == NULL,
                               install_list);
 
   // Copy over brand, usagestats, and other values.
   AddGoogleUpdateWorkItems(original_state, installer_state, install_list);
 
+  // Migrate usagestats back to Chrome.
+  AddMigrateUsageStatesWorkItems(original_state, installer_state, install_list);
+
   // Append the tasks that run after the installation.
   AppendPostInstallTasks(installer_state,
                          setup_path,
                          current_version,
                          new_version,
                          temp_path,
                          install_list);
 }
 
 void AddRegisterComDllWorkItems(const base::FilePath& dll_folder,
@@ skipping 297 matching lines @@
   // Unconditionally remove the legacy Quick Enable command from the binaries.
   // Do this even if multi-install Chrome isn't installed to ensure that it is
   // not left behind in any case.
   work_item_list->AddDeleteRegKeyWorkItem(
                       installer_state.root_key(), cmd_key, KEY_WOW64_32KEY)
       ->set_log_message("removing " + base::UTF16ToASCII(kCmdQuickEnableCf) +
                         " command");
 }
 
 }  // namespace installer