Cleanup: Put more chrome/ code behind ENABLE_EXTENSIONS ifdefs.

chrome/browser/ui/browser.h

Index: chrome/browser/ui/browser.h
diff --git a/chrome/browser/ui/browser.h b/chrome/browser/ui/browser.h
index 2e17be1f8196abcdccebd6fd466e039aea62e594..6ff0707ff017358975c2cdbbabf0d20554b32dcd 100644
--- a/chrome/browser/ui/browser.h
+++ b/chrome/browser/ui/browser.h
@@ -39,13 +39,16 @@
 #include "content/public/browser/page_navigator.h"
 #include "content/public/browser/web_contents_delegate.h"
 #include "content/public/common/page_zoom.h"
-#include "extensions/browser/extension_registry_observer.h"
 #include "ui/base/page_transition_types.h"
 #include "ui/base/ui_base_types.h"
 #include "ui/base/window_open_disposition.h"
 #include "ui/gfx/rect.h"
 #include "ui/shell_dialogs/select_file_dialog.h"
 
+#if defined(ENABLE_EXTENSIONS)
+#include "extensions/browser/extension_registry_observer.h"
+#endif
+
 class BrowserContentSettingBubbleModelDelegate;
 class BrowserContentTranslateDriverObserver;
 class BrowserInstantController;
@@ -108,7 +111,9 @@ class Browser : public TabStripModelObserver,
                 public ZoomObserver,
                 public content::PageNavigator,
                 public content::NotificationObserver,
+#if defined(ENABLE_EXTENSIONS)
                 public extensions::ExtensionRegistryObserver,
+#endif
                 public ui::SelectFileDialog::Listener {
  public:
   // SessionService::WindowType mirrors these values.  If you add to this
@@ -716,6 +721,7 @@ class Browser : public TabStripModelObserver,
                        const content::NotificationSource& source,
                        const content::NotificationDetails& details) override;
 
+#if defined(ENABLE_EXTENSIONS)
   // Overridden from extensions::ExtensionRegistryObserver:
   virtual void OnExtensionUninstalled(
       content::BrowserContext* browser_context,
@@ -728,6 +734,7 @@ class Browser : public TabStripModelObserver,
       content::BrowserContext* browser_context,
       const extensions::Extension* extension,
       extensions::UnloadedExtensionInfo::Reason reason) override;
+#endif
 
   // Command and state updating ///////////////////////////////////////////////
 
@@ -842,9 +849,11 @@ class Browser : public TabStripModelObserver,
 
   content::NotificationRegistrar registrar_;
 
+#if defined(ENABLE_EXTENSIONS)
   ScopedObserver<extensions::ExtensionRegistry,
                  extensions::ExtensionRegistryObserver>
       extension_registry_observer_;
+#endif
 
   PrefChangeRegistrar profile_pref_registrar_;