Always suffix ChromeHTML entries on Windows for user-level installs.

chrome/installer/util/shell_util.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 defines functions that integrate Chrome in Windows shell. These
 // functions can be used by Chrome as well as Chrome installer. All of the
 // work is done by the local functions defined in anonymous namespace in
 // this class.
 
 #include "chrome/installer/util/shell_util.h"
@@ skipping 56 matching lines @@
   return VerifyVersionInfo(&min_version_info, type_mask, condition_mask) != 0;
 }
 
 // This class represents a single registry entry. The objective is to
 // encapsulate all the registry entries required for registering Chrome at one
 // place. This class can not be instantiated outside the class and the objects
 // of this class type can be obtained only by calling a static method of this
 // class.
 class RegistryEntry {
  public:
+  // A bit-field enum of places to look for this key in the Windows registry.
+  enum LookForIn {
+    LOOK_IN_HKCU = 1 << 0,
+    LOOK_IN_HKLM = 1 << 1,
+  };
+
   // Returns the Windows browser client registration key for Chrome.  For
   // example: "Software\Clients\StartMenuInternet\Chromium[.user]".  Strictly
   // speaking, we should use the name of the executable (e.g., "chrome.exe"),
   // but that ship has sailed.  The cost of switching now is re-prompting users
   // to make Chrome their default browser, which isn't polite.  |suffix| is the
   // user-specific registration suffix; see GetUserSpecificDefaultBrowserSuffix
   // in shell_util.h for details.
   static string16 GetBrowserClientKey(BrowserDistribution* dist,
                                       const string16& suffix) {
     DCHECK(suffix.empty() || suffix[0] == L'.');
     return string16(ShellUtil::kRegStartMenuInternet)
         .append(1, L'\\')
         .append(dist->GetApplicationName())
         .append(suffix);
   }
 
   // Returns the Windows Default Programs capabilities key for Chrome.  For
   // example:
   // "Software\Clients\StartMenuInternet\Chromium[.user]\Capabilities".
   static string16 GetCapabilitiesKey(BrowserDistribution* dist,
                                      const string16& suffix) {
     return GetBrowserClientKey(dist, suffix).append(L"\\Capabilities");
   }
 
+  // Returns true if Chrome is registered with the given |suffix| either in HKCU
+  // or HKLM.
+  // This function only checks for the existence of
+  // Software\Classes\ChromeHTML|suffix| and doesn't otherwise validate the
+  // registration of Chrome.
+  static bool IsChromeRegisteredWithSuffix(const string16& suffix) {
+    DCHECK(!suffix.empty());
+    string16 chrome_html_prog_id(ShellUtil::kRegClasses);
+    chrome_html_prog_id.push_back(FilePath::kSeparators[0]);
+    chrome_html_prog_id.append(ShellUtil::kChromeHTMLProgId);
+    chrome_html_prog_id.append(suffix);
+    return RegistryEntry(chrome_html_prog_id,
+                         ShellUtil::kChromeHTMLProgIdDesc).ExistsInRegistry(
+                             LOOK_IN_HKCU & LOOK_IN_HKLM);
+  }
+
   // This method returns a list of all the registry entries that
   // are needed to register Chromium ProgIds.
   // These entries should be registered in HKCU for user-level installs and in
   // HKLM for system-level installs.
   // TODO (gab): Extract the Windows 8 only registrations out of this function.
   static bool GetProgIdEntries(BrowserDistribution* dist,
                                const string16& chrome_exe,
                                const string16& suffix,
                                std::list<RegistryEntry*>* entries) {
     string16 icon_path(ShellUtil::GetChromeIcon(dist, chrome_exe));
@@ skipping 132 matching lines @@
     // strings.
     entries->push_front(new RegistryEntry(install_info, kReinstallCommand,
         quoted_exe_path + L" --" + ASCIIToWide(switches::kMakeDefaultBrowser)));
     entries->push_front(new RegistryEntry(install_info, L"HideIconsCommand",
         quoted_exe_path + L" --" + ASCIIToWide(switches::kHideIcons)));
     entries->push_front(new RegistryEntry(install_info, L"ShowIconsCommand",
         quoted_exe_path + L" --" + ASCIIToWide(switches::kShowIcons)));
     entries->push_front(new RegistryEntry(install_info, L"IconsVisible", 1));
 
     // Register with Default Programs.
-    string16 app_name(dist->GetApplicationName().append(suffix));
+    string16 reg_app_name(dist->GetApplicationName().append(suffix));
     // Tell Windows where to find Chrome's Default Programs info.
     string16 capabilities(GetCapabilitiesKey(dist, suffix));
     entries->push_front(new RegistryEntry(ShellUtil::kRegRegisteredApplications,
-        app_name, capabilities));
+        reg_app_name, capabilities));
     // Write out Chrome's Default Programs info.
     // TODO(grt): http://crbug.com/75152 Write a reference to a localized
     // resource rather than this.
     entries->push_front(new RegistryEntry(
         capabilities, ShellUtil::kRegApplicationDescription,
         dist->GetLongAppDescription()));
     entries->push_front(new RegistryEntry(
         capabilities, ShellUtil::kRegApplicationIcon, icon_path));
     entries->push_front(new RegistryEntry(
-        capabilities, ShellUtil::kRegApplicationName, app_name));
+        capabilities, ShellUtil::kRegApplicationName,
+        dist->GetApplicationName()));
 
     entries->push_front(new RegistryEntry(capabilities + L"\\Startmenu",
-        L"StartMenuInternet", app_name));
+        L"StartMenuInternet", reg_app_name));
 
     string16 html_prog_id(ShellUtil::kChromeHTMLProgId);
     html_prog_id.append(suffix);
     for (int i = 0; ShellUtil::kFileAssociations[i] != NULL; i++) {
       entries->push_front(new RegistryEntry(
           capabilities + L"\\FileAssociations",
           ShellUtil::kFileAssociations[i], html_prog_id));
     }
     for (int i = 0; ShellUtil::kPotentialProtocolAssociations[i] != NULL;
         i++) {
@@ skipping 89 matching lines @@
     if (_is_string) {
       items->AddSetRegValueWorkItem(root, _key_path, _name, _value, true);
     } else {
       items->AddSetRegValueWorkItem(root, _key_path, _name, _int_value, true);
     }
   }
 
   // Checks if the current registry entry exists in HKCU\|_key_path|\|_name|
   // and value is |_value|. If the key does NOT exist in HKCU, checks for
   // the correct name and value in HKLM.
-  // This mimics Windows' behavior when searching in HKCR (HKCU takes precedence
-  // over HKLM). For registrations outside of HKCR on versions of Windows up
-  // to Win7, Chrome's values go in HKLM. This function will make unnecessary
-  // (but harmless) queries into HKCU in that case. Starting with Windows 8,
-  // Chrome's values go in HKCU for user-level installs, which takes precedence
-  // over HKLM.
-  bool ExistsInRegistry() {
-    RegistryStatus hkcu_status = StatusInRegistryUnderRoot(HKEY_CURRENT_USER);
+  // |look_for_in| specifies roots (HKCU and/or HKLM) in which to look for the
+  // key, unspecified roots are not looked in and the key is assumed not to
+  // exist in them.
+  // |look_for_in| must at least specify one root to look into.
+  // If |look_for_in| specifies both HKCU and HKLM, this method mimics Windows'
+  // behavior when searching in HKCR (HKCU takes precedence over HKLM). For
+  // registrations outside of HKCR on versions of Windows up to Win7, Chrome's
+  // values go in HKLM. This function will make unnecessary (but harmless)
+  // queries into HKCU in that case. Starting with Windows 8, Chrome's values go
+  // in HKCU for user-level installs, which takes precedence over HKLM.
+  bool ExistsInRegistry(uint32 look_for_in) const {
+    DCHECK(look_for_in);
+
+    RegistryStatus hkcu_status = DOES_NOT_EXIST;
+    if (look_for_in & LOOK_IN_HKCU)
+      hkcu_status = StatusInRegistryUnderRoot(HKEY_CURRENT_USER);
+
+    RegistryStatus hklm_status = DOES_NOT_EXIST;
+    if (hkcu_status == DOES_NOT_EXIST && (look_for_in & LOOK_IN_HKLM))
+      hklm_status = StatusInRegistryUnderRoot(HKEY_LOCAL_MACHINE);
+
     return (hkcu_status == SAME_VALUE ||
-            (hkcu_status == DOES_NOT_EXIST &&
-             StatusInRegistryUnderRoot(HKEY_LOCAL_MACHINE) == SAME_VALUE));
+            (hkcu_status == DOES_NOT_EXIST && hklm_status == SAME_VALUE));
   }
 
  private:
   // States this RegistryKey can be in compared to the registry.
   enum RegistryStatus {
     // |_name| does not exist in the registry
     DOES_NOT_EXIST,
     // |_name| exists, but its value != |_value|
     DIFFERENT_VALUE,
     // |_name| exists and its value is |_value|
@@ skipping 63 matching lines @@
 
   // Apply all the registry changes and if there is a problem, rollback
   if (!items->Do()) {
     items->Rollback();
     return false;
   }
   return true;
 }
 
 // Checks that all |entries| are present on this computer.
-bool AreEntriesRegistered(const std::list<RegistryEntry*>& entries) {
+// |look_for_in| is passed to RegistryEntry::ExistsInRegistry(). Documentation
+// for it can be found there.
+bool AreEntriesRegistered(const std::list<RegistryEntry*>& entries,
+                          uint32 look_for_in) {
   bool registered = true;
   for (std::list<RegistryEntry*>::const_iterator itr = entries.begin();
        registered && itr != entries.end(); ++itr) {
     // We do not need registered = registered && ... since the loop condition
     // is set to exit early.
-    registered = (*itr)->ExistsInRegistry();
+    registered = (*itr)->ExistsInRegistry(look_for_in);
   }
   return registered;
 }
 
 // Checks that all required registry entries for Chrome are already present
 // on this computer.
 bool IsChromeRegistered(BrowserDistribution* dist,
                         const string16& chrome_exe,
                         const string16& suffix) {
   std::list<RegistryEntry*> entries;
   STLElementDeleter<std::list<RegistryEntry*> > entries_deleter(&entries);
   RegistryEntry::GetProgIdEntries(dist, chrome_exe, suffix, &entries);
   RegistryEntry::GetSystemEntries(dist, chrome_exe, suffix, &entries);
-  return AreEntriesRegistered(entries);
+  return AreEntriesRegistered(
+      entries, RegistryEntry::LOOK_IN_HKCU & RegistryEntry::LOOK_IN_HKLM);
 }
 
 // This method checks if Chrome is already registered on the local machine
 // for the requested protocol. It just checks the one value required for this.
 bool IsChromeRegisteredForProtocol(BrowserDistribution* dist,
                                    const string16& suffix,
                                    const string16& protocol) {
   std::list<RegistryEntry*> entries;
   STLElementDeleter<std::list<RegistryEntry*> > entries_deleter(&entries);
   RegistryEntry::GetProtocolCapabilityEntries(dist, suffix, protocol, &entries);
-  return AreEntriesRegistered(entries);
+  return AreEntriesRegistered(
+      entries, RegistryEntry::LOOK_IN_HKCU & RegistryEntry::LOOK_IN_HKLM);
 }
 
 // This method registers Chrome on Vista by launching an elevated setup.exe.
 // That will show the user the standard Vista elevation prompt. If the user
 // accepts it the new process will make the necessary changes and return SUCCESS
 // that we capture and return.
 // If protocol is non-empty we will also register Chrome as being capable of
 // handling the protocol.
 bool ElevateAndRegisterChrome(BrowserDistribution* dist,
                               const string16& chrome_exe,
@@ skipping 32 matching lines @@
     }
 
     DWORD ret_val = 0;
     InstallUtil::ExecuteExeAsAdmin(cmd, &ret_val);
     if (ret_val == 0)
       return true;
   }
   return false;
 }
 
-// This method tries to figure out if another user has already registered her
-// own copy of Chrome so that we can avoid overwriting it and append current
-// user's login name to default browser registry entries. This function is
-// not meant to detect all cases. It just tries to handle the most common case.
-// All the conditions below have to be true for it to return true:
-// - Software\Clients\StartMenuInternet\Chromium\"" key should have a valid
-//   value.
-// - The value should not be same as given value in |chrome_exe|
-// - Finally to handle the default install path (C:\Document and Settings\
-//   <user>\Local Settings\Application Data\Chromium\Application) the value
-//   of the above key should differ from |chrome_exe| only in user name.
-bool AnotherUserHasDefaultBrowser(BrowserDistribution* dist,
-                                  const string16& chrome_exe) {
-  const string16 reg_key(
-      RegistryEntry::GetBrowserClientKey(dist, string16())
-      .append(ShellUtil::kRegShellOpen));
-  RegKey key(HKEY_LOCAL_MACHINE, reg_key.c_str(), KEY_READ);
-  string16 registry_chrome_exe;
-  if ((key.ReadValue(L"", &registry_chrome_exe) != ERROR_SUCCESS) ||
-      registry_chrome_exe.length() < 2)
-    return false;
-
-  registry_chrome_exe = registry_chrome_exe.substr(1,
-      registry_chrome_exe.length() - 2);
-  if ((registry_chrome_exe.size() == chrome_exe.size()) &&
-      (std::equal(chrome_exe.begin(), chrome_exe.end(),
-                  registry_chrome_exe.begin(),
-                  base::CaseInsensitiveCompare<wchar_t>()))) {
-    return false;
-  }
-
-  std::vector<string16> v1, v2;
-  base::SplitString(registry_chrome_exe, L'\\', &v1);
-  base::SplitString(chrome_exe, L'\\', &v2);
-  if (v1.empty() || v2.empty() || v1.size() != v2.size())
-    return false;
-
-  // Now check that only one of the values within two '\' chars differ.
-  std::vector<string16>::iterator itr1 = v1.begin();
-  std::vector<string16>::iterator itr2 = v2.begin();
-  bool one_mismatch = false;
-  for ( ; itr1 < v1.end() && itr2 < v2.end(); ++itr1, ++itr2) {
-    string16 s1 = *itr1;
-    string16 s2 = *itr2;
-    if ((s1.size() != s2.size()) ||
-        (!std::equal(s1.begin(), s1.end(),
-                     s2.begin(), base::CaseInsensitiveCompare<wchar_t>()))) {
-      if (one_mismatch)
-        return false;
-      else
-        one_mismatch = true;
-    }
-  }
-  return true;
-}
-
 // Launches the Windows 7 and Windows 8 application association dialog, which
 // is the only documented way to make a browser the default browser on
 // Windows 8.
 bool LaunchApplicationAssociationDialog(const string16& app_id) {
   base::win::ScopedComPtr<IApplicationAssociationRegistrationUI> aarui;
   HRESULT hr = aarui.CreateInstance(CLSID_ApplicationAssociationRegistrationUI);
   if (FAILED(hr))
     return false;
   hr = aarui->LaunchAdvancedAssociationUI(app_id.c_str());
   return SUCCEEDED(hr);
@@ skipping 46 matching lines @@
     key = ShellUtil::kRegClasses;
     key.push_back(FilePath::kSeparators[0]);
     key.append(ShellUtil::kChromeHTMLProgId);
     key.append(suffix);
     key.append(ShellUtil::kRegShellOpen);
     InstallUtil::DeleteRegistryValue(root_key, key,
                                      ShellUtil::kRegDelegateExecute);
   }
 }
 
+// Returns true if the current user-level install has been registered without
+// a suffix. This is used to support old installs where we used to not suffix
+// user-level installs if they were the first to request the non-suffixed
+// registry entries on the machine. This however created clashes with
+// system-level installs when updating user-level installs to system-level
+// installs. There is no downside to suffixing anyways (the name registered is
+// not user visible).
+// All the conditions below have to be true for it to return true:
+// - Software\Clients\StartMenuInternet\Chromium\"" key should have a valid
+//   value.
+// - The value should be same as given value in |chrome_exe|.
+bool CurrentUserIsRegisteredWithNoSuffix(BrowserDistribution* dist,
+                                       const string16& chrome_exe) {
+  // Assert that a Chrome is registered under
+  // HKLM\Software\Clients\StartMenuInternet\Google Chrome
+  const string16 reg_key(
+      RegistryEntry::GetBrowserClientKey(dist, string16())
+      .append(ShellUtil::kRegShellOpen));
+  RegKey key(HKEY_LOCAL_MACHINE, reg_key.c_str(), KEY_READ);
+  string16 registry_chrome_exe;
+  if ((key.ReadValue(L"", &registry_chrome_exe) != ERROR_SUCCESS) ||
+      registry_chrome_exe.length() < 2) {
+    return false;
+  }
+
+  // Assert that the Chrome registered there is |chrome_exe| (i.e. this user's
+  // Chrome).
+  registry_chrome_exe = registry_chrome_exe.substr(1,
+      registry_chrome_exe.length() - 2);
+  if (registry_chrome_exe.size() != chrome_exe.size() ||
+      !std::equal(chrome_exe.begin(), chrome_exe.end(),
+                  registry_chrome_exe.begin(),
+                  base::CaseInsensitiveCompare<wchar_t>())) {
+    return false;
+  }
+
+  return true;
+}
+
+// Sets |suffix| to this user's username preceded by a dot. This suffix is then
+// meant to be added to all registration that may conflict with another
+// user-level Chrome install.
+// Returns true unless the OS call to retrieve the username fails.
+bool GetUserSpecificRegistrySuffix(string16* suffix) {
+  wchar_t user_name[256];
+  DWORD size = arraysize(user_name);
+  if (::GetUserName(user_name, &size) == 0 || size < 1) {
+    LOG(DFATAL) << "Failed to get username in " << __FUNCTION__ << ".";
+    return false;
+  }
+  suffix->reserve(size);
+  suffix->assign(1, L'.');
+  suffix->append(user_name, size - 1);
+  return true;
+}
+
+// Sets |suffix| to the current user's username on user-level installs.
+// To support old-style user-level installs however, |suffix| is cleared if
+// the user currently owns the non-suffixed HKLM registrations.
+// |suffix| is also cleared on system-level installs.
+// |suffix| should then be appended to all Chrome properties that may conflict
+// with other Chrome user-level installs.
+// Returns true unless one of the underlying calls fails.
+bool GetInstallationSpecificSuffix(BrowserDistribution* dist,
+                                   const string16& chrome_exe,
+                                   string16* suffix) {
+  if (!InstallUtil::IsPerUserInstall(chrome_exe.c_str()) ||
+      CurrentUserIsRegisteredWithNoSuffix(dist, chrome_exe)) {
+    // No suffix on system-level installs and user-level installs already
+    // registered with no suffix.
+    *suffix = L"";
+    return true;
+  } else {
+    return GetUserSpecificRegistrySuffix(suffix);
+  }
+}
+
 }  // namespace
 
 const wchar_t* ShellUtil::kRegDefaultIcon = L"\\DefaultIcon";
 const wchar_t* ShellUtil::kRegShellPath = L"\\shell";
 const wchar_t* ShellUtil::kRegShellOpen = L"\\shell\\open\\command";
 const wchar_t* ShellUtil::kRegStartMenuInternet =
     L"Software\\Clients\\StartMenuInternet";
 const wchar_t* ShellUtil::kRegClasses = L"Software\\Classes";
 const wchar_t* ShellUtil::kRegRegisteredApplications =
     L"Software\\RegisteredApplications";
@@ skipping 226 matching lines @@
                  KEY_QUERY_VALUE) != ERROR_SUCCESS ||
         key.ReadValue(kReinstallCommand, &command) != ERROR_SUCCESS) {
       continue;
     }
     if (!name.empty() && !command.empty() &&
         name.find(dist->GetApplicationName()) == string16::npos)
       (*browsers)[name] = command;
   }
 }
 
-bool ShellUtil::GetUserSpecificDefaultBrowserSuffix(BrowserDistribution* dist,
-                                                    string16* entry) {
-  wchar_t user_name[256];
-  DWORD size = arraysize(user_name);
-  if (::GetUserName(user_name, &size) == 0 || size < 1)
-    return false;
-  entry->reserve(size);
-  entry->assign(1, L'.');
-  entry->append(user_name, size - 1);
+string16 ShellUtil::GetCurrentInstallationSuffix() {
+  string16 tested_suffix;
+  if (!GetUserSpecificRegistrySuffix(&tested_suffix) ||
+      !RegistryEntry::IsChromeRegisteredWithSuffix(tested_suffix)) {
+    return L"";
+  }
+  return tested_suffix;
+}
 
-  return RegKey(HKEY_LOCAL_MACHINE,
-                RegistryEntry::GetBrowserClientKey(dist, *entry).c_str(),
-                KEY_READ).Valid();
+bool ShellUtil::IsInstallationPresentInHKLM(BrowserDistribution* dist,
+                                            const string16& chrome_exe,
+                                            const string16& suffix) {
+  std::list<RegistryEntry*> entries;
+  STLElementDeleter<std::list<RegistryEntry*> > entries_deleter(&entries);
+  RegistryEntry::GetSystemEntries(dist, chrome_exe, suffix, &entries);
+  return AreEntriesRegistered(entries, RegistryEntry::LOOK_IN_HKLM);
 }
 
 bool ShellUtil::MakeChromeDefault(BrowserDistribution* dist,
                                   int shell_change,
                                   const string16& chrome_exe,
                                   bool elevate_if_not_admin) {
   if (!dist->CanSetAsDefault())
     return false;
 
   ShellUtil::RegisterChromeBrowser(dist, chrome_exe, L"", elevate_if_not_admin);
 
   bool ret = true;
   // First use the new "recommended" way on Vista to make Chrome default
   // browser.
   string16 app_name = dist->GetApplicationName();
-  string16 app_suffix;
-  if (ShellUtil::GetUserSpecificDefaultBrowserSuffix(dist, &app_suffix))
-    app_name += app_suffix;
+  const string16 app_suffix(ShellUtil::GetCurrentInstallationSuffix());
+  app_name += app_suffix;
 
   if (base::win::GetVersion() >= base::win::VERSION_WIN8) {
     // On Windows 8, you can't set yourself as the default handler
     // programatically. In other words IApplicationAssociationRegistration
     // has been rendered useless. What you can do is to launch
     // "Set Program Associations" section of the "Default Programs"
     // control panel. This action does not require elevation and we
     // don't get to control window activation. More info at:
     // http://msdn.microsoft.com/en-us/library/cc144154(VS.85).aspx
     return LaunchApplicationAssociationDialog(app_name.c_str());
@@ skipping 29 matching lines @@
     }
   }
 
   // Now use the old way to associate Chrome with supported protocols and file
   // associations. This should not be required on Vista but since some
   // applications still read Software\Classes\http key directly, we have to do
   // this on Vista also.
 
   std::list<RegistryEntry*> entries;
   STLElementDeleter<std::list<RegistryEntry*> > entries_deleter(&entries);
-  string16 suffix;
-  if (!GetUserSpecificDefaultBrowserSuffix(dist, &suffix))
-    suffix = L"";
-  RegistryEntry::GetUserEntries(dist, chrome_exe, suffix, &entries);
+  RegistryEntry::GetUserEntries(dist, chrome_exe, app_suffix, &entries);
   // Change the default browser for current user.
   if ((shell_change & ShellUtil::CURRENT_USER) &&
       !AddRegistryEntries(HKEY_CURRENT_USER, entries)) {
     ret = false;
     LOG(ERROR) << "Could not make Chrome default browser (XP/current user).";
   }
 
   // Chrome as default browser at system level.
   if ((shell_change & ShellUtil::SYSTEM_LEVEL) &&
       !AddRegistryEntries(HKEY_LOCAL_MACHINE, entries)) {
@@ skipping 19 matching lines @@
   // First use the new "recommended" way on Vista to make Chrome default
   // protocol handler.
   if (base::win::GetVersion() >= base::win::VERSION_VISTA) {
     VLOG(1) << "Registering Chrome as default handler for " << protocol
             << " on Vista.";
     base::win::ScopedComPtr<IApplicationAssociationRegistration> pAAR;
     HRESULT hr = pAAR.CreateInstance(CLSID_ApplicationAssociationRegistration,
       NULL, CLSCTX_INPROC);
     if (SUCCEEDED(hr)) {
       string16 app_name = dist->GetApplicationName();
-      string16 suffix;
-      if (ShellUtil::GetUserSpecificDefaultBrowserSuffix(dist, &suffix))
-        app_name += suffix;
+      app_name += ShellUtil::GetCurrentInstallationSuffix();
 
       hr = pAAR->SetAppAsDefault(app_name.c_str(), protocol.c_str(),
                                  AT_URLPROTOCOL);
     }
     if (!SUCCEEDED(hr)) {
       ret = false;
       LOG(ERROR) << "Could not make Chrome default protocol client (Vista):"
                  << " HRESULT=" << hr << ".";
     }
   }
 
   // Now use the old way to associate Chrome with the desired protocol. This
   // should not be required on Vista but since some applications still read
   // Software\Classes\http key directly, we have to do this on Vista also.
 
   std::list<RegistryEntry*> entries;
   STLElementDeleter<std::list<RegistryEntry*> > entries_deleter(&entries);
-  string16 suffix;
-  if (!GetUserSpecificDefaultBrowserSuffix(dist, &suffix))
-    suffix = L"";
-  string16 chrome_open = ShellUtil::GetChromeShellOpenCmd(chrome_exe);
-  string16 chrome_icon = ShellUtil::GetChromeIcon(dist, chrome_exe);
+  const string16 suffix(ShellUtil::GetCurrentInstallationSuffix());
+  const string16 chrome_open(ShellUtil::GetChromeShellOpenCmd(chrome_exe));
+  const string16 chrome_icon(ShellUtil::GetChromeIcon(dist, chrome_exe));
   RegistryEntry::GetUserProtocolEntries(protocol, chrome_icon, chrome_open,
                                         &entries);
   // Change the default protocol handler for current user.
   if (!AddRegistryEntries(HKEY_CURRENT_USER, entries)) {
       ret = false;
       LOG(ERROR) << "Could not make Chrome default protocol client (XP).";
   }
 
   return ret;
 }
 
 bool ShellUtil::RegisterChromeBrowser(BrowserDistribution* dist,
                                       const string16& chrome_exe,
                                       const string16& unique_suffix,
                                       bool elevate_if_not_admin) {
   if (!dist->CanSetAsDefault())
     return false;
 
-  // First figure out we need to append a suffix to the registry entries to
-  // make them unique.
   string16 suffix;
   if (!unique_suffix.empty()) {
     suffix = unique_suffix;
-  } else if (InstallUtil::IsPerUserInstall(chrome_exe.c_str()) &&
-             !GetUserSpecificDefaultBrowserSuffix(dist, &suffix) &&
-             !AnotherUserHasDefaultBrowser(dist, chrome_exe)) {
-    suffix = L"";
+  } else if (!GetInstallationSpecificSuffix(dist, chrome_exe, &suffix)) {
+    return false;
   }
 
   // TODO(grt): remove this on or after 2012-08-01; see impl for details.
   RemoveBadWindows8RegistrationIfNeeded(dist, chrome_exe, suffix);
 
   // Check if Chromium is already registered with this suffix.
   if (IsChromeRegistered(dist, chrome_exe, suffix))
     return true;
 
   // If user is an admin try to register and return the status.
@@ skipping 10 matching lines @@
                progids) &&
            AddRegistryEntries(HKEY_LOCAL_MACHINE, sys_entries);
   }
 
   // If user is not an admin and OS is Vista, try to elevate and register.
   if (elevate_if_not_admin &&
       base::win::GetVersion() >= base::win::VERSION_VISTA &&
       ElevateAndRegisterChrome(dist, chrome_exe, suffix, L""))
     return true;
 
-  // If we got to this point then all we can do is create ProgIds under HKCU
-  // on XP as well as Vista.
+  // If we got to this point then all we can do is create ProgIds under HKCU.
   std::list<RegistryEntry*> entries;
   STLElementDeleter<std::list<RegistryEntry*> > entries_deleter(&entries);
   RegistryEntry::GetProgIdEntries(dist, chrome_exe, L"", &entries);
+  // Prefer to use |suffix|; unless Chrome's ProgIds are already registered with
+  // no suffix (as per the old registration style): in which case some other
+  // registry entries could refer to them and since we were not able to set our
+  // HKLM entries above, we are better off not altering these here.
+  if (!suffix.empty() &&
+      !AreEntriesRegistered(entries, RegistryEntry::LOOK_IN_HKCU)) {
+    entries.clear();
+    RegistryEntry::GetProgIdEntries(dist, chrome_exe, suffix, &entries);
+  }
   return AddRegistryEntries(HKEY_CURRENT_USER, entries);
 }
 
 bool ShellUtil::RegisterChromeForProtocol(BrowserDistribution* dist,
                                           const string16& chrome_exe,
                                           const string16& unique_suffix,
                                           const string16& protocol,
                                           bool elevate_if_not_admin) {
   if (!dist->CanSetAsDefault())
     return false;
 
-  // Figure out we need to append a suffix to the registry entries to
-  // make them unique.
   string16 suffix;
   if (!unique_suffix.empty()) {
     suffix = unique_suffix;
-  } else if (InstallUtil::IsPerUserInstall(chrome_exe.c_str()) &&
-             !GetUserSpecificDefaultBrowserSuffix(dist, &suffix) &&
-             !AnotherUserHasDefaultBrowser(dist, chrome_exe)) {
-    suffix = L"";
+  } else if (!GetInstallationSpecificSuffix(dist, chrome_exe, &suffix)) {
+    return false;
   }
 
   // Check if Chromium is already registered with this suffix.
   if (IsChromeRegisteredForProtocol(dist, suffix, protocol))
     return true;
 
   if (IsUserAnAdmin()) {
     // We can do this operation directly.
     // If we're not registered at all, try to register. If that fails
     // we should give up.
@@ skipping 125 matching lines @@
       chrome_exe.c_str(),
       shortcut.c_str(),
       chrome_path.c_str(),
       arguments.c_str(),
       description.c_str(),
       icon_path.c_str(),
       icon_index,
       dist->GetBrowserAppId().c_str(),
       ConvertShellUtilShortcutOptionsToFileUtil(options));
 }