Convert enable_plugins to a buildflag header.

content/browser/web_contents/web_contents_impl.h

Index: content/browser/web_contents/web_contents_impl.h
diff --git a/content/browser/web_contents/web_contents_impl.h b/content/browser/web_contents/web_contents_impl.h
index aeeeebda43542495c94e91b29c4c7f71db477280..b740b9ba86aeea7466d566900f042afcf4d31363 100644
--- a/content/browser/web_contents/web_contents_impl.h
+++ b/content/browser/web_contents/web_contents_impl.h
@@ -44,6 +44,7 @@
 #include "content/public/common/three_d_api_types.h"
 #include "net/base/load_states.h"
 #include "net/http/http_response_headers.h"
+#include "ppapi/features/features.h"
 #include "third_party/WebKit/public/platform/WebDragOperation.h"
 #include "ui/base/page_transition_types.h"
 #include "ui/gfx/geometry/rect_f.h"
@@ -99,7 +100,7 @@ class CreateNewWindowParams;
 class WebContentsAndroid;
 #endif
 
-#if defined(ENABLE_PLUGINS)
+#if BUILDFLAG(ENABLE_PLUGINS)
 class PepperPlaybackObserver;
 #endif
 
@@ -979,7 +980,7 @@ class CONTENT_EXPORT WebContentsImpl
                    const std::string& name,
                    const base::ListValue& args);
   void OnUpdatePageImportanceSignals(const PageImportanceSignals& signals);
-#if defined(ENABLE_PLUGINS)
+#if BUILDFLAG(ENABLE_PLUGINS)
   void OnPepperInstanceCreated(int32_t pp_instance);
   void OnPepperInstanceDeleted(int32_t pp_instance);
   void OnPepperPluginHung(int plugin_child_id,
@@ -999,7 +1000,7 @@ class CONTENT_EXPORT WebContentsImpl
 
   void OnBrowserPluginMessage(RenderFrameHost* render_frame_host,
                               const IPC::Message& message);
-#endif  // defined(ENABLE_PLUGINS)
+#endif  // BUILDFLAG(ENABLE_PLUGINS)
   void OnUpdateFaviconURL(const std::vector<FaviconURL>& candidates);
   void OnFirstVisuallyNonEmptyPaint();
   void OnShowValidationMessage(const gfx::Rect& anchor_in_root_view,
@@ -1363,7 +1364,7 @@ class CONTENT_EXPORT WebContentsImpl
   // NULL otherwise.
   std::unique_ptr<BrowserPluginGuest> browser_plugin_guest_;
 
-#if defined(ENABLE_PLUGINS)
+#if BUILDFLAG(ENABLE_PLUGINS)
   // Manages the whitelist of plugin content origins exempt from power saving.
   std::unique_ptr<PluginContentOriginWhitelist>
       plugin_content_origin_whitelist_;
@@ -1440,10 +1441,10 @@ class CONTENT_EXPORT WebContentsImpl
   // Manages media players, CDMs, and power save blockers for media.
   std::unique_ptr<MediaWebContentsObserver> media_web_contents_observer_;
 
-#if defined(ENABLE_PLUGINS)
+#if BUILDFLAG(ENABLE_PLUGINS)
   // Observes pepper playback changes, and notifies MediaSession.
   std::unique_ptr<PepperPlaybackObserver> pepper_playback_observer_;
-#endif  // defined(ENABLE_PLUGINS)
+#endif  // BUILDFLAG(ENABLE_PLUGINS)
 
   std::unique_ptr<HostZoomMapObserver> host_zoom_map_observer_;