feat: [extensions] support extension.getBackgroundPage (#21951)

* feat: [extensions] support extension.getBackgroundPage

* cleanup

* how does c++

* tests

* test for runtime.getBackgroundPage too

shell/browser/electron_browser_client.cc

@@ -186,6 +186,63 @@ const base::FilePath::StringPieceType kPathDelimiter = FILE_PATH_LITERAL(";");
 const base::FilePath::StringPieceType kPathDelimiter = FILE_PATH_LITERAL(":");
 #endif
 
+#if BUILDFLAG(ENABLE_ELECTRON_EXTENSIONS)
+// Used by the GetPrivilegeRequiredByUrl() and GetProcessPrivilege() functions
+// below.  Extension, and isolated apps require different privileges to be
+// granted to their RenderProcessHosts.  This classification allows us to make
+// sure URLs are served by hosts with the right set of privileges.
+enum RenderProcessHostPrivilege {
+  PRIV_NORMAL,
+  PRIV_HOSTED,
+  PRIV_ISOLATED,
+  PRIV_EXTENSION,
+};
+
+RenderProcessHostPrivilege GetPrivilegeRequiredByUrl(
+    const GURL& url,
+    extensions::ExtensionRegistry* registry) {
+  // Default to a normal renderer cause it is lower privileged. This should only
+  // occur if the URL on a site instance is either malformed, or uninitialized.
+  // If it is malformed, then there is no need for better privileges anyways.
+  // If it is uninitialized, but eventually settles on being an a scheme other
+  // than normal webrenderer, the navigation logic will correct us out of band
+  // anyways.
+  if (!url.is_valid())
+    return PRIV_NORMAL;
+
+  if (!url.SchemeIs(extensions::kExtensionScheme))
+    return PRIV_NORMAL;
+
+  return PRIV_EXTENSION;
+}
+
+RenderProcessHostPrivilege GetProcessPrivilege(
+    content::RenderProcessHost* process_host,
+    extensions::ProcessMap* process_map,
+    extensions::ExtensionRegistry* registry) {
+  std::set<std::string> extension_ids =
+      process_map->GetExtensionsInProcess(process_host->GetID());
+  if (extension_ids.empty())
+    return PRIV_NORMAL;
+
+  return PRIV_EXTENSION;
+}
+
+const extensions::Extension* GetEnabledExtensionFromEffectiveURL(
+    content::BrowserContext* context,
+    const GURL& effective_url) {
+  if (!effective_url.SchemeIs(extensions::kExtensionScheme))
+    return nullptr;
+
+  extensions::ExtensionRegistry* registry =
+      extensions::ExtensionRegistry::Get(context);
+  if (!registry)
+    return nullptr;
+
+  return registry->enabled_extensions().GetByID(effective_url.host());
+}
+#endif  // BUILDFLAG(ENABLE_ELECTRON_EXTENSIONS)
+
 }  // namespace
 
 // static
@@ -760,6 +817,40 @@ void ElectronBrowserClient::SiteInstanceGotProcess(
 #endif  // BUILDFLAG(ENABLE_ELECTRON_EXTENSIONS)
 }
 
+bool ElectronBrowserClient::IsSuitableHost(
+    content::RenderProcessHost* process_host,
+    const GURL& site_url) {
+#if BUILDFLAG(ENABLE_ELECTRON_EXTENSIONS)
+  auto* browser_context = process_host->GetBrowserContext();
+  extensions::ExtensionRegistry* registry =
+      extensions::ExtensionRegistry::Get(browser_context);
+  extensions::ProcessMap* process_map =
+      extensions::ProcessMap::Get(browser_context);
+
+  // Otherwise, just make sure the process privilege matches the privilege
+  // required by the site.
+  RenderProcessHostPrivilege privilege_required =
+      GetPrivilegeRequiredByUrl(site_url, registry);
+  return GetProcessPrivilege(process_host, process_map, registry) ==
+         privilege_required;
+#else
+  return content::ContentBrowserClient::IsSuitableHost(process_host, site_url);
+#endif
+}
+
+bool ElectronBrowserClient::ShouldUseProcessPerSite(
+    content::BrowserContext* browser_context,
+    const GURL& effective_url) {
+#if BUILDFLAG(ENABLE_ELECTRON_EXTENSIONS)
+  const extensions::Extension* extension =
+      GetEnabledExtensionFromEffectiveURL(browser_context, effective_url);
+  return extension != nullptr;
+#else
+  return content::ContentBrowserClient::ShouldUseProcessPerSite(browser_context,
+                                                                effective_url);
+#endif
+}
+
 void ElectronBrowserClient::SiteInstanceDeleting(
     content::SiteInstance* site_instance) {
   // We are storing weak_ptr, is it fundamental to maintain the map up-to-date