Parse the script_badge manifest section.

chrome/browser/extensions/script_badge_controller.cc

Index: chrome/browser/extensions/script_badge_controller.cc
diff --git a/chrome/browser/extensions/script_badge_controller.cc b/chrome/browser/extensions/script_badge_controller.cc
index 7efd6a99a4e32176d5c80e69c245e44681624ff8..ce93f45d2d12c6467eeb687dfa513f6ac5b778d5 100644
--- a/chrome/browser/extensions/script_badge_controller.cc
+++ b/chrome/browser/extensions/script_badge_controller.cc
@@ -11,6 +11,7 @@
 #include "chrome/common/extensions/extension_action.h"
 #include "chrome/common/extensions/extension_messages.h"
 #include "chrome/common/extensions/extension_set.h"
+#include "chrome/common/extensions/extension_switch_utils.h"
 #include "chrome/common/chrome_notification_types.h"
 #include "content/public/browser/navigation_controller.h"
 #include "content/public/browser/navigation_entry.h"
@@ -24,7 +25,10 @@ namespace extensions {
 ScriptBadgeController::ScriptBadgeController(TabContents* tab_contents)
     : content::WebContentsObserver(tab_contents->web_contents()),
       script_executor_(tab_contents->web_contents()),
-      tab_contents_(tab_contents) {}
+      tab_contents_(tab_contents) {
+  CHECK(switch_utils::IsActionBoxEnabled())
+      << "Without this, extension->script_badge() would return NULL.";

[not at google - send to devlin, 2012/06/18 18:51:24]

Is this necessary? We only construct these objects when this flag (soon-to-be
enable-script-badges) is true. If anything, (D)CHECK below that script_badge
returns non-NULL.

[Jeffrey Yasskin, 2012/06/18 22:16:03]

The CHECK is intended to tell people reading the code that you only construct
these objects when this flag is true. As the code was, I had to ask you. I could
remove the "Without this..." comment if you want.

[not at google - send to devlin, 2012/06/18 22:59:41]

Maybe just a comment would be more appropriate then?

// Note: this class will only be constructed from ExtensionTabHelper if
// script badges have been enabled.

or something. And a DCHECK if you really want.

[Jeffrey Yasskin, 2012/06/18 23:58:41]

I put the comment inside the DCHECK.

For future reference, what's the convention for deciding between CHECK and
DCHECK when flagging impossible situations?

[not at google - send to devlin, 2012/06/19 00:27:32]

I think of DCHECK as documentation and CHECK as bug-catching.

So in this case, if ScriptBadgeController was instantiated without that flag, no
biggie. But it can't possibly be because forces outside its control never do so.

[Jeffrey Yasskin, 2012/06/19 21:43:08]

Now that script_badge() always returns non-NULL, I think the CHECK isn't needed,
and it requires the switch-overriding machinery, so it's gone.

+}
 
 ScriptBadgeController::~ScriptBadgeController() {}
 
@@ -41,7 +45,7 @@ ScriptBadgeController::GetCurrentActions() {
        it != service->extensions()->end(); ++it) {
     const Extension* extension = *it;
     if (extensions_executing_scripts_.count(extension->id()))
-      current_actions->push_back(extension->GetScriptBadge());
+      current_actions->push_back(extension->script_badge());
   }
   return current_actions.Pass();
 }