web_browser: Take ECommerce applet frontend optionally in constructor

If it is needed but wasn't passed (or passed nullptr), the Shop handling code will alert and throw an error.

src/core/hle/service/am/applets/web_browser.h

@@ -17,7 +17,9 @@ enum class WebArgTLVType : u16;
 
 class WebBrowser final : public Applet {
 public:
-    WebBrowser(Core::Frontend::WebBrowserApplet& frontend);
+    WebBrowser(Core::Frontend::WebBrowserApplet& frontend,
+               Core::Frontend::ECommerceApplet* frontend_e_commerce = nullptr);
+
     ~WebBrowser() override;
 
     void Initialize() override;
@@ -50,6 +52,9 @@ private:
 
     Core::Frontend::WebBrowserApplet& frontend;
 
+    // Extra frontends for specialized functions
+    Core::Frontend::ECommerceApplet* frontend_e_commerce;
+
     bool complete = false;
     bool unpacked = false;
     ResultCode status = RESULT_SUCCESS;