Convert enable_plugins to a buildflag header.

chrome/browser/apps/guest_view/web_view_browsertest.cc

Index: chrome/browser/apps/guest_view/web_view_browsertest.cc
diff --git a/chrome/browser/apps/guest_view/web_view_browsertest.cc b/chrome/browser/apps/guest_view/web_view_browsertest.cc
index 0328c36ef8d3d1ed504f3f17d88eed9f055eb361..340a9b9b27f878a3ef211b4a88886e6a6b7f319d 100644
--- a/chrome/browser/apps/guest_view/web_view_browsertest.cc
+++ b/chrome/browser/apps/guest_view/web_view_browsertest.cc
@@ -77,6 +77,7 @@
 #include "net/test/embedded_test_server/embedded_test_server.h"
 #include "net/test/embedded_test_server/http_request.h"
 #include "net/test/embedded_test_server/http_response.h"
+#include "ppapi/features/features.h"
 #include "ui/aura/env.h"
 #include "ui/aura/window.h"
 #include "ui/compositor/compositor.h"
@@ -88,7 +89,7 @@
 #include "ui/views/view.h"
 #include "ui/views/widget/widget.h"
 
-#if defined(ENABLE_PLUGINS)
+#if BUILDFLAG(ENABLE_PLUGINS)
 #include "content/public/browser/plugin_service.h"
 #include "content/public/common/webplugininfo.h"
 #include "content/public/test/ppapi_test_utils.h"
@@ -2986,7 +2987,7 @@ IN_PROC_BROWSER_TEST_P(WebViewTest, NoContentSettingsAPI) {
   TestHelper("testPostMessageCommChannel", "web_view/shim", NO_TEST_SERVER);
 }
 
-#if defined(ENABLE_PLUGINS)
+#if BUILDFLAG(ENABLE_PLUGINS)
 class WebViewPluginTest : public WebViewTest {
  protected:
   void SetUpCommandLine(base::CommandLine* command_line) override {
@@ -3012,7 +3013,7 @@ IN_PROC_BROWSER_TEST_P(WebViewPluginTest, TestLoadPluginInternalResource) {
 
   TestHelper("testPluginLoadInternalResource", "web_view/shim", NO_TEST_SERVER);
 }
-#endif  // defined(ENABLE_PLUGINS)
+#endif  // BUILDFLAG(ENABLE_PLUGINS)
 
 class WebViewCaptureTest : public WebViewTest {
  public: