Try 2: Completely redo how themes are stored on disk and processed at install time.

chrome/common/pref_names.cc

 // Copyright (c) 2009 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.
 
 #include "chrome/common/pref_names.h"
 
 namespace prefs {
 
 // *************** PROFILE PREFS ***************
 // These are attached to the user profile
@@ skipping 232 matching lines @@
 const wchar_t kPrintingPageHeaderLeft[] = L"printing.page.header.left";
 const wchar_t kPrintingPageHeaderCenter[] = L"printing.page.header.center";
 const wchar_t kPrintingPageHeaderRight[] = L"printing.page.header.right";
 const wchar_t kPrintingPageFooterLeft[] = L"printing.page.footer.left";
 const wchar_t kPrintingPageFooterCenter[] = L"printing.page.footer.center";
 const wchar_t kPrintingPageFooterRight[] = L"printing.page.footer.right";
 #if defined(OS_LINUX)
 // GTK specific preference on whether we should match the system GTK theme.
 const wchar_t kUsesSystemTheme[] = L"extensions.theme.use_system";
 #endif
+const wchar_t kCurrentThemePackFilename[] = L"extensions.theme.pack";
 const wchar_t kCurrentThemeID[] = L"extensions.theme.id";
 const wchar_t kCurrentThemeImages[] = L"extensions.theme.images";
 const wchar_t kCurrentThemeColors[] = L"extensions.theme.colors";
 const wchar_t kCurrentThemeTints[] = L"extensions.theme.tints";
 const wchar_t kCurrentThemeDisplayProperties[] =
     L"extensions.theme.properties";
 
 // Boolean pref which persists whether the extensions_ui is in developer mode
 // (showing developer packing tools and extensions details)
 const wchar_t kExtensionsUIDeveloperMode[] = L"extensions.ui.developer_mode";
@@ skipping 341 matching lines @@
 const wchar_t kSyncHasSetupCompleted[] = L"sync.has_setup_completed";
 
 // Create web application shortcut dialog preferences.
 const wchar_t kWebAppCreateOnDesktop[] = L"browser.web_app.create_on_desktop";
 const wchar_t kWebAppCreateInAppsMenu[] =
     L"browser.web_app.create_in_apps_menu";
 const wchar_t kWebAppCreateInQuickLaunchBar[] =
     L"browser.web_app.create_in_quick_launch_bar";
 
 }  // namespace prefs