Only build extensions code in chrome/browser/ui when extensions are enabled.

chrome/browser/extensions/extension_system_impl.cc

Index: chrome/browser/extensions/extension_system_impl.cc
diff --git a/chrome/browser/extensions/extension_system_impl.cc b/chrome/browser/extensions/extension_system_impl.cc
index 8e853085a61f02dd8832c245a020d400157fcb1f..ee61be99148f93dd989c94b9f2205dc536f742c0 100644
--- a/chrome/browser/extensions/extension_system_impl.cc
+++ b/chrome/browser/extensions/extension_system_impl.cc
@@ -30,7 +30,6 @@
 #include "chrome/browser/extensions/user_script_master.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/profiles/profile_manager.h"
-#include "chrome/browser/ui/webui/extensions/extension_icon_source.h"
 #include "chrome/common/chrome_switches.h"
 #include "chrome/common/chrome_version_info.h"
 #include "chrome/common/extensions/extension_constants.h"
@@ -61,6 +60,7 @@
 
 #if defined(ENABLE_EXTENSIONS)
 #include "chrome/browser/extensions/unpacked_installer.h"
+#include "chrome/browser/ui/webui/extensions/extension_icon_source.h"
 #endif
 
 #if defined(ENABLE_NOTIFICATIONS)
@@ -364,8 +364,10 @@ void ExtensionSystemImpl::Shared::Init(bool extensions_enabled) {
   }
   extension_service_->Init();
 
+#if defined(ENABLE_EXTENSIONS)
   // Make the chrome://extension-icon/ resource available.
   content::URLDataSource::Add(profile_, new ExtensionIconSource(profile_));
+#endif
 
   extension_warning_service_.reset(new ExtensionWarningService(profile_));
   extension_warning_badge_service_.reset(