Cleanup: Prevent usage of various extension headers when extensions support is not compiled in.

chrome/browser/sync/glue/extensions_activity_monitor.cc

Index: chrome/browser/sync/glue/extensions_activity_monitor.cc
diff --git a/chrome/browser/sync/glue/extensions_activity_monitor.cc b/chrome/browser/sync/glue/extensions_activity_monitor.cc
index b7b23912c5c75a64606fc68ffb9bc0ad8bec9e10..287bc9a7e38c913f9ca5edbdb093502687a257b4 100644
--- a/chrome/browser/sync/glue/extensions_activity_monitor.cc
+++ b/chrome/browser/sync/glue/extensions_activity_monitor.cc
@@ -4,13 +4,15 @@
 
 #include "chrome/browser/sync/glue/extensions_activity_monitor.h"
 
-#include "base/bind.h"
+#include "content/public/browser/browser_thread.h"
+#include "sync/util/extensions_activity.h"
+
+#if defined(ENABLE_EXTENSIONS)
 #include "chrome/browser/chrome_notification_types.h"
 #include "chrome/browser/extensions/api/bookmarks/bookmarks_api.h"
-#include "content/public/browser/browser_thread.h"
 #include "content/public/browser/notification_service.h"
 #include "extensions/common/extension.h"
-#include "sync/util/extensions_activity.h"
+#endif
 
 using content::BrowserThread;
 
@@ -18,26 +20,30 @@ namespace browser_sync {
 
 ExtensionsActivityMonitor::ExtensionsActivityMonitor()
     : extensions_activity_(new syncer::ExtensionsActivity()) {
-  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+  DCHECK_CURRENTLY_ON(BrowserThread::UI);
   // It would be nice if we could specify a Source for each specific function
   // we wanted to observe, but the actual function objects are allocated on
   // the fly so there is no reliable object to point to (same problem if we
   // wanted to use the string name).  Thus, we use all sources and filter in
   // Observe.
+#if defined(ENABLE_EXTENSIONS)
   registrar_.Add(this,
                  extensions::NOTIFICATION_EXTENSION_BOOKMARKS_API_INVOKED,
                  content::NotificationService::AllSources());
+#endif
 }
 
 ExtensionsActivityMonitor::~ExtensionsActivityMonitor() {
-  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+  DCHECK_CURRENTLY_ON(BrowserThread::UI);
 }
 
 void ExtensionsActivityMonitor::Observe(
     int type,
     const content::NotificationSource& source,
     const content::NotificationDetails& details) {
-  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+#if defined(ENABLE_EXTENSIONS)
+  DCHECK_CURRENTLY_ON(BrowserThread::UI);
+  DCHECK_EQ(extensions::NOTIFICATION_EXTENSION_BOOKMARKS_API_INVOKED, type);
   const extensions::Extension* extension =
       content::Source<const extensions::Extension>(source).ptr();
   const extensions::BookmarksFunction* f =
@@ -49,6 +55,7 @@ void ExtensionsActivityMonitor::Observe(
       f->name() == "bookmarks.remove") {
     extensions_activity_->UpdateRecord(extension->id());
   }
+#endif
 }
 
 const scoped_refptr<syncer::ExtensionsActivity>&