Adds a basic offline check to InstallableManager.

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 c095f9d1314c7fe028441bb19479c2f73d4fc99e..1c194babe470aea980e68f742e2fc2c3fb3a7ce8 100644
--- a/content/public/browser/service_worker_context.h
+++ b/content/public/browser/service_worker_context.h
@@ -18,6 +18,12 @@ enum class WebNavigationHintType;
 
 namespace content {
 
+enum class ServiceWorkerCapability {
+  NO_SERVICE_WORKER,
+  SERVICE_WORKER_NO_FETCH_HANDLER,
+  SERVICE_WORKER_WITH_FETCH_HANDLER,
+};
+
 // Represents the per-StoragePartition ServiceWorker data.
 class ServiceWorkerContext {
  public:
@@ -31,7 +37,7 @@ class ServiceWorkerContext {
       const std::vector<ServiceWorkerUsageInfo>& usage_info)>;
 
   using CheckHasServiceWorkerCallback =
-      base::Callback<void(bool has_service_worker)>;
+      base::Callback<void(ServiceWorkerCapability capability)>;
 
   using CountExternalRequestsCallback =
       base::Callback<void(size_t external_request_count)>;
@@ -102,10 +108,14 @@ class ServiceWorkerContext {
   virtual void DeleteForOrigin(const GURL& origin_url,
                                const ResultCallback& callback) = 0;
 
-  // Returns true if a Service Worker registration exists that matches |url|,
-  // and if |other_url| falls inside the scope of the same registration. Note
-  // this still returns true even if there is a Service Worker registration
-  // which has a longer match for |other_url|.
+  // Returns ServiceWorkerCapability describing existence and properties of a
+  // Service Worker registration matching |url|. Found service worker
+  // registration must also encompass the |other_url|, otherwise it will be
+  // considered non existent by this method. Note that this doesn't ensure to
+  // describe a Service Worker registration with the longest possible match for
+  // |other_url|. In case the service worker is being installed as of calling

[falken, 2017/03/21 01:53:24]

Thanks for expanding this comment! For some reason I have trouble reading:
"this doesn't ensure to describe a Service Worker registration with the longest
possible match for |other_url|"

Is the following better?
"Note that the longest matching registration for |url| is described, which is
not necessarily the longest matching registration for |other_url|."

[piotrs, 2017/03/21 02:12:49]

Done.

+  // this method, it will wait for the installation to finish before coming back
+  // with the result.
   //
   // This function can be called from any thread, but the callback will always
   // be called on the UI thread.