This is essentially just a similarity=50 version of https://codereview.chromium.org/95133002/ and i…

chrome/browser/ui/views/toolbar/browser_action_view.cc

Index: chrome/browser/ui/views/toolbar/browser_action_view.cc
diff --git a/chrome/browser/ui/views/toolbar/browser_action_view.cc b/chrome/browser/ui/views/toolbar/browser_action_view.cc
index 14a7bbbb0eae150c6969d9097873edb9372ea48f..8d153390a5ab36da7a091eababe1967d048690d5 100644
--- a/chrome/browser/ui/views/toolbar/browser_action_view.cc
+++ b/chrome/browser/ui/views/toolbar/browser_action_view.cc
@@ -7,9 +7,11 @@
 #include "base/strings/utf_string_conversions.h"
 #include "chrome/browser/chrome_notification_types.h"
 #include "chrome/browser/extensions/api/commands/command_service.h"
+#include "chrome/browser/extensions/dev_mode_bubble_controller.h"
 #include "chrome/browser/extensions/extension_action.h"
 #include "chrome/browser/extensions/extension_action_manager.h"
 #include "chrome/browser/extensions/extension_context_menu_model.h"
+#include "chrome/browser/extensions/extension_service.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/themes/theme_service.h"
 #include "chrome/browser/themes/theme_service_factory.h"
@@ -238,7 +240,14 @@ void BrowserActionButton::UpdateState() {
     ThemeService* theme =
         ThemeServiceFactory::GetForProfile(browser_->profile());
 
-    gfx::ImageSkia bg = *theme->GetImageSkiaNamed(IDR_BROWSER_ACTION);
+    int background_id = IDR_BROWSER_ACTION;
+    extensions::DevModeBubbleController* controller =
+        extensions::DevModeBubbleController::Get(
+            browser_->profile());
+    if (controller->IsDevModeExtension(extension_))
+      background_id = IDR_BROWSER_ACTION_HIGHLIGHT;
+
+    gfx::ImageSkia bg = *theme->GetImageSkiaNamed(background_id);
     SetIcon(gfx::ImageSkiaOperations::CreateSuperimposedImage(bg, icon));
 
     gfx::ImageSkia bg_h = *theme->GetImageSkiaNamed(IDR_BROWSER_ACTION_H);