Disable extensions besides externally installed ones and themes.

chrome/browser/renderer_host/browser_render_process_host.cc

Index: chrome/browser/renderer_host/browser_render_process_host.cc
diff --git a/chrome/browser/renderer_host/browser_render_process_host.cc b/chrome/browser/renderer_host/browser_render_process_host.cc
index 06405ed8efcdbbeeadac3f206159b96e10c02b26..2463b39d0e257626de2ebe0a06de093cc3116701 100644
--- a/chrome/browser/renderer_host/browser_render_process_host.cc
+++ b/chrome/browser/renderer_host/browser_render_process_host.cc
@@ -30,6 +30,7 @@
 #include "chrome/browser/browser_process.h"
 #include "chrome/browser/child_process_security_policy.h"
 #include "chrome/browser/extensions/extension_message_service.h"
+#include "chrome/browser/extensions/extensions_service.h"
 #include "chrome/browser/extensions/user_script_master.h"
 #include "chrome/browser/history/history.h"
 #include "chrome/browser/plugin_service.h"
@@ -273,7 +274,6 @@ bool BrowserRenderProcessHost::Init() {
     switches::kUseLowFragHeapCrt,
     switches::kEnableWebWorkers,
     switches::kEnableStatsTable,
-    switches::kEnableExtensions,
     switches::kDisableOutOfProcessDevTools,
     switches::kAutoSpellCorrect,
     switches::kDisableAudio,
@@ -288,6 +288,25 @@ bool BrowserRenderProcessHost::Init() {
     }
   }
 
+  // Tell the renderer to enable extensions if there are any extensions loaded.
+  //
+  // NOTE: This is subtly different than just passing along whether
+  // --enable-extenisons is present in the browser process. For example, there
+  // is also an extensions.enabled preference, and there may be various special
+  // cases about whether to allow extensions to load. 
+  //
+  // This introduces a race condition where the first renderer never gets
+  // extensions enabled, so we also set the flag if extensions_enabled(). This
+  // isn't perfect though, because of the special cases above.
+  //
+  // TODO(aa): We need to get rid of the need to pass this flag at all. It is
+  // only used in one place in the renderer.
+  if (profile()->GetExtensionsService()) {
+    if (profile()->GetExtensionsService()->extensions()->size() > 0 ||
+        profile()->GetExtensionsService()->extensions_enabled())
+      cmd_line.AppendSwitch(switches::kEnableExtensions);
+  }
+
   // Pass on the browser locale.
   const std::wstring locale = g_browser_process->GetApplicationLocale();
   cmd_line.AppendSwitchWithValue(switches::kLang, locale);