Fix intermittent failure JsSkusBrowserTest.AttachSkus (#30791)

Fix for the render frame observer which is created on the stack in the
test file, but its `OnDestruct` calls `delete this;`

https://github.com/brave/brave-core/commit/9d896aaa5d0b0873434bee37a92f89e78e8661fe#diff-9b6f35d6bb55585416f5c5b7f[…]531e094f6039534e46870f267e84R68
Added the `delete this;`

And then a later commit added the test which created it on the stack:
https://github.com/brave/brave-core/commit/0a03ac5defcc619296085cdd8e4654521efe6ec5#diff-10e48a4b1e39427a1c98f8882[…]4d712ff32b2affd45df70ee319e2R35

i

components/skus/renderer/skus_render_frame_observer.cc

@@ -18,6 +18,12 @@
 
 namespace skus {
 
+// static
+SkusRenderFrameObserver* SkusRenderFrameObserver::Create(
+    content::RenderFrame* render_frame) {
+  return new SkusRenderFrameObserver(render_frame);
+}
+
 SkusRenderFrameObserver::SkusRenderFrameObserver(
     content::RenderFrame* render_frame)
     : RenderFrameObserver(render_frame) {}

components/skus/renderer/skus_render_frame_observer.h

@@ -6,8 +6,6 @@
 #ifndef BRAVE_COMPONENTS_SKUS_RENDERER_SKUS_RENDER_FRAME_OBSERVER_H_
 #define BRAVE_COMPONENTS_SKUS_RENDERER_SKUS_RENDER_FRAME_OBSERVER_H_
 
-#include <memory>
-
 #include "brave/components/skus/renderer/skus_js_handler.h"
 #include "content/public/renderer/render_frame.h"
 #include "content/public/renderer/render_frame_observer.h"
@@ -25,15 +23,17 @@ namespace skus {
 // See `browser/brave_content_browser_client.cc` for more information.
 class SkusRenderFrameObserver : public content::RenderFrameObserver {
  public:
-  explicit SkusRenderFrameObserver(content::RenderFrame* render_frame);
+  static SkusRenderFrameObserver* Create(content::RenderFrame* render_frame);
   SkusRenderFrameObserver(const SkusRenderFrameObserver&) = delete;
   SkusRenderFrameObserver& operator=(const SkusRenderFrameObserver&) = delete;
-  ~SkusRenderFrameObserver() override;
 
   // RenderFrameObserver implementation.
   void DidClearWindowObject() override;
 
  private:
+  explicit SkusRenderFrameObserver(content::RenderFrame* render_frame);
+  ~SkusRenderFrameObserver() override;
+
   // RenderFrameObserver implementation.
   void OnDestruct() override;
 

renderer/brave_content_renderer_client.cc

@@ -178,7 +178,7 @@ void BraveContentRendererClient::RenderFrameCreated(
 
   if (base::FeatureList::IsEnabled(skus::features::kSkusFeature) &&
       !IsIncognitoProcess()) {
-    new skus::SkusRenderFrameObserver(render_frame);
+    skus::SkusRenderFrameObserver::Create(render_frame);
   }
 
 #if BUILDFLAG(IS_ANDROID)

renderer/skus/js_skus_browsertest.cc

@@ -30,7 +30,7 @@ class JsSkusBrowserTest : public content::RenderViewTest {
 };
 
 TEST_F(JsSkusBrowserTest, AttachSkus) {
-  SkusRenderFrameObserver observer(GetMainRenderFrame());
+  SkusRenderFrameObserver::Create(GetMainRenderFrame());
   std::u16string command =
       u"Number((window.chrome !== undefined) && (window.chrome.braveSkus !== "
       u"undefined) && "