Move enable extensions define to a build flag.

chrome/browser/download/download_history_unittest.cc

Index: chrome/browser/download/download_history_unittest.cc
diff --git a/chrome/browser/download/download_history_unittest.cc b/chrome/browser/download/download_history_unittest.cc
index 04a22bf56d5e498cbb83c5be617422f1f863dfd1..f692be61089b910ec4e32ab4f82497545f4972ed 100644
--- a/chrome/browser/download/download_history_unittest.cc
+++ b/chrome/browser/download/download_history_unittest.cc
@@ -23,9 +23,10 @@
 #include "content/public/test/mock_download_manager.h"
 #include "content/public/test/test_browser_thread.h"
 #include "content/public/test/test_utils.h"
+#include "extensions/features/features.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
-#if defined(ENABLE_EXTENSIONS)
+#if BUILDFLAG(ENABLE_EXTENSIONS)
 #include "chrome/browser/extensions/api/downloads/downloads_api.h"
 #endif
 
@@ -437,7 +438,7 @@ class DownloadHistoryTest : public testing::Test {
     EXPECT_CALL(manager(), GetDownload(id))
         .WillRepeatedly(Return(&item(index)));
     EXPECT_CALL(item(index), IsTemporary()).WillRepeatedly(Return(false));
-#if defined(ENABLE_EXTENSIONS)
+#if BUILDFLAG(ENABLE_EXTENSIONS)
     new extensions::DownloadedByExtension(
         &item(index), by_extension_id, by_extension_name);
 #endif