Add a ServiceWorkerContextObserver to content's public API.

content/public/browser/service_worker_context.h

Index: content/public/browser/service_worker_context.h
diff --git a/content/public/browser/service_worker_context.h b/content/public/browser/service_worker_context.h
index 22d13f9bd57ac84e19382a9430fc1a88f20b0199..35bbf822498bdb8bc1bf49fff3642553c2d7c60e 100644
--- a/content/public/browser/service_worker_context.h
+++ b/content/public/browser/service_worker_context.h
@@ -14,6 +14,8 @@
 
 namespace content {
 
+class ServiceWorkerContextObserver;
+
 enum class ServiceWorkerCapability {
   NO_SERVICE_WORKER,
   SERVICE_WORKER_NO_FETCH_HANDLER,
@@ -47,6 +49,13 @@ class ServiceWorkerContext {
   // Must be called from the IO thread.
   static bool IsExcludedHeaderNameForFetchEvent(const std::string& header_name);
 
+  // Returns true if |url| is within the service worker |scope|.
+  CONTENT_EXPORT static bool ScopeMatches(const GURL& scope, const GURL& url);
+
+  // Observer methods are always dispatched on the UI thread.
+  virtual void AddObserver(ServiceWorkerContextObserver* observer) = 0;
+  virtual void RemoveObserver(ServiceWorkerContextObserver* observer) = 0;
+
   // Equivalent to calling navigator.serviceWorker.register(script_url, {scope:
   // pattern}) from a renderer, except that |pattern| is an absolute URL instead
   // of relative to some current origin.  |callback| is passed true when the JS