Revert of Pass the v8::Context through the willDestroyServiceWorkerContextOnWorkerThread event. (patchset #3 id:60001 of https://codereview.chromium.org/1318643002/ )

Reason for revert:
Canary is frequently crashing, likely due to threading issues with this patch.

Original issue's description:
> Pass the v8::Context through the willDestroyServiceWorkerContextOnWorkerThread event.
>
> Currently it only passes a URL, and this isn't enough to uniquely identify the worker.
> Update extension's dispatcher.cc to use the context.
>
> BUG=501569, 525965
> R=kinuko@chromium.org, thestig@chromium.org
>
> Committed: https://crrev.com/4a0bb926cb1d83fab27b6ad866c04ba481f66268
> Cr-Commit-Position: refs/heads/master@{#346424}

TBR=thestig@chromium.org,kinuko@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=501569, 525965

Review URL: https://codereview.chromium.org/1319603003

Cr-Commit-Position: refs/heads/master@{#346978}

2 files changed, 14 insertions, 57 deletions

diff --git a/extensions/renderer/dispatcher.cc b/extensions/renderer/dispatcher.cc
index 1203e6f..34324e2 100644
--- a/extensions/renderer/dispatcher.cc
+++ b/extensions/renderer/dispatcher.cc
@@ -197,41 +197,21 @@ class ServiceWorkerScriptContextSet {
   ServiceWorkerScriptContextSet() {}
   ~ServiceWorkerScriptContextSet() {}
 
-  void Insert(scoped_ptr<ScriptContext> context) {
+  void Insert(const GURL& url, scoped_ptr<ScriptContext> context) {
     base::AutoLock lock(lock_);
-    CHECK(FindScriptContext(context->v8_context()) == contexts_.end());
-    contexts_.push_back(context.Pass());
+    CHECK(script_contexts_.find(url) == script_contexts_.end());
+    script_contexts_.set(url, context.Pass());
   }
 
-  void Remove(v8::Local<v8::Context> v8_context) {
+  void Remove(const GURL& url) {
     base::AutoLock lock(lock_);
-    ScriptContextList::iterator context_it = FindScriptContext(v8_context);
-    // TODO(kalman): It would be good to CHECK(context_it != contexts_.end())
-    // here, but service workers can be started before the extension has been
-    // installed. See the length comment explaining why this happens, and
-    // how to solve it, in DidInitializeServiceWorkerContextOnWorkerThread.
-    // This does need to be fixed eventually, but for now, at least don't crash.
-    if (context_it == contexts_.end())
-      return;
-    (*context_it)->Invalidate();
-    contexts_.erase(context_it);
+    scoped_ptr<ScriptContext> context = script_contexts_.take_and_erase(url);
+    CHECK(context);
+    context->Invalidate();
   }
 
  private:
-  using ScriptContextList = ScopedVector<ScriptContext>;
-
-  // Returns an iterator to the ScriptContext associated with |v8_context|, or
-  // contexts_.end() if not found.
-  ScriptContextList::iterator FindScriptContext(
-      v8::Local<v8::Context> v8_context) {
-    for (auto it = contexts_.begin(); it != contexts_.end(); ++it) {
-      if ((*it)->v8_context() == v8_context)
-        return it;
-    }
-    return contexts_.end();
-  }
-
-  ScriptContextList contexts_;
+  base::ScopedPtrMap<GURL, scoped_ptr<ScriptContext>> script_contexts_;
 
   mutable base::Lock lock_;
 
@@ -403,35 +383,15 @@ void Dispatcher::DidInitializeServiceWorkerContextOnWorkerThread(
   const Extension* extension =
       RendererExtensionRegistry::Get()->GetExtensionOrAppByURL(url);
 
-  if (!extension) {
-    // TODO(kalman): This is no good. Instead we need to either:
-    //
-    // - Hold onto the v8::Context and create the ScriptContext and install
-    //   our bindings when this extension is loaded.
-    // - Deal with there being an extension ID (url.host()) but no
-    //   extension associated with it, then document that getBackgroundClient
-    //   may fail if the extension hasn't loaded yet.
-    //
-    // The former is safer, but is unfriendly to caching (e.g. session restore).
-    // It seems to contradict the service worker idiom.
-    //
-    // The latter is friendly to caching, but running extension code without an
-    // installed extension makes me nervous, and means that we won't be able to
-    // expose arbitrary (i.e. capability-checked) extension APIs to service
-    // workers. We will probably need to relax some assertions - we just need
-    // to find them.
-    //
-    // Perhaps this could be solved with our own event on the service worker
-    // saying that an extension is ready, and documenting that extension APIs
-    // won't work before that event has fired?
+  if (!extension)
     return;
-  }
 
   ScriptContext* context = new ScriptContext(
       v8_context, nullptr, extension, Feature::SERVICE_WORKER_CONTEXT,
       extension, Feature::SERVICE_WORKER_CONTEXT);
 
-  g_service_worker_script_context_set.Get().Insert(make_scoped_ptr(context));
+  g_service_worker_script_context_set.Get().Insert(url,
+                                                   make_scoped_ptr(context));
 
   v8::Isolate* isolate = context->isolate();
 
@@ -478,10 +438,9 @@ void Dispatcher::WillReleaseScriptContext(
 
 // static
 void Dispatcher::WillDestroyServiceWorkerContextOnWorkerThread(
-    v8::Local<v8::Context> v8_context,
     const GURL& url) {
-  if (url.SchemeIs(kExtensionScheme))
-    g_service_worker_script_context_set.Get().Remove(v8_context);
+  if (RendererExtensionRegistry::Get()->GetExtensionOrAppByURL(url))
+    g_service_worker_script_context_set.Get().Remove(url);
 }
 
 void Dispatcher::DidCreateDocumentElement(blink::WebLocalFrame* frame) {
diff --git a/extensions/renderer/dispatcher.h b/extensions/renderer/dispatcher.h
index fb1714d..428efd7 100644
--- a/extensions/renderer/dispatcher.h
+++ b/extensions/renderer/dispatcher.h
@@ -102,9 +102,7 @@ class Dispatcher : public content::RenderProcessObserver,
                                 int world_id);
 
   // Runs on a different thread and should not use any member variables.
-  static void WillDestroyServiceWorkerContextOnWorkerThread(
-      v8::Local<v8::Context> v8_context,
-      const GURL& url);
+  static void WillDestroyServiceWorkerContextOnWorkerThread(const GURL& url);
 
   void DidCreateDocumentElement(blink::WebLocalFrame* frame);