Convert enable_plugins to a buildflag header.

chrome/browser/metrics/chrome_stability_metrics_provider.cc

Index: chrome/browser/metrics/chrome_stability_metrics_provider.cc
diff --git a/chrome/browser/metrics/chrome_stability_metrics_provider.cc b/chrome/browser/metrics/chrome_stability_metrics_provider.cc
index 59171c9fe6332dbf2b4d9e537c7441428795257d..0bc625a077601dd0981603c4e1f299e6b97e8124 100644
--- a/chrome/browser/metrics/chrome_stability_metrics_provider.cc
+++ b/chrome/browser/metrics/chrome_stability_metrics_provider.cc
@@ -15,12 +15,13 @@
 #include "content/public/browser/notification_service.h"
 #include "content/public/browser/render_process_host.h"
 #include "extensions/features/features.h"
+#include "ppapi/features/features.h"
 
 #if BUILDFLAG(ENABLE_EXTENSIONS)
 #include "extensions/browser/process_map.h"
 #endif
 
-#if defined(ENABLE_PLUGINS)
+#if BUILDFLAG(ENABLE_PLUGINS)
 #include "chrome/browser/metrics/plugin_metrics_provider.h"
 #endif
 
@@ -122,7 +123,7 @@ void ChromeStabilityMetricsProvider::Observe(
 void ChromeStabilityMetricsProvider::BrowserChildProcessCrashed(
     const content::ChildProcessData& data,
     int exit_code) {
-#if defined(ENABLE_PLUGINS)
+#if BUILDFLAG(ENABLE_PLUGINS)
   // Exclude plugin crashes from the count below because we report them via
   // a separate UMA metric.
   if (PluginMetricsProvider::IsPluginProcess(data.process_type))