shared worker: Simplify telling devtools about start and stop of worker.

SharedWorkerHost was calling WorkedDestroyed at three callsites using
two flags to determine when to do so. Use a RAII helper class to manage
the state instead.

One motiviation is fixing 830288 which is going to add more state to
SharedWorkerHost (creating a host before calling start), so when to call
WorkerDestroyed would get more complicated.

Bug: 830288
Change-Id: Ie3f135d925091518b172a4afcd8c475656aa9db4
Reviewed-on: https://chromium-review.googlesource.com/1013360Reviewed-by: Hiroki Nakagawa <nhiroki@chromium.org>
Commit-Queue: Matt Falkenhagen <falken@chromium.org>
Cr-Commit-Position: refs/heads/master@{#550958}

content/browser/shared_worker/shared_worker_host.cc

@@ -54,6 +54,31 @@ bool AllowIndexedDBOnIOThread(const GURL& url,
 
 }  // namespace
 
+// RAII helper class for talking to SharedWorkerDevToolsManager.
+class SharedWorkerHost::ScopedDevToolsHandle {
+ public:
+  ScopedDevToolsHandle(SharedWorkerHost* owner,
+                       bool* out_pause_on_start,
+                       base::UnguessableToken* out_devtools_worker_token)
+      : owner_(owner) {
+    SharedWorkerDevToolsManager::GetInstance()->WorkerCreated(
+        owner, out_pause_on_start, out_devtools_worker_token);
+  }
+
+  ~ScopedDevToolsHandle() {
+    SharedWorkerDevToolsManager::GetInstance()->WorkerDestroyed(owner_);
+  }
+
+  void WorkerReadyForInspection() {
+    SharedWorkerDevToolsManager::GetInstance()->WorkerReadyForInspection(
+        owner_);
+  }
+
+ private:
+  SharedWorkerHost* owner_;
+  DISALLOW_COPY_AND_ASSIGN(ScopedDevToolsHandle);
+};
+
 SharedWorkerHost::SharedWorkerHost(
     SharedWorkerServiceImpl* service,
     std::unique_ptr<SharedWorkerInstance> instance,
@@ -72,8 +97,6 @@ SharedWorkerHost::SharedWorkerHost(
 SharedWorkerHost::~SharedWorkerHost() {
   UMA_HISTOGRAM_LONG_TIMES("SharedWorker.TimeToDeleted",
                            base::TimeTicks::Now() - creation_time_);
-  if (!closed_ && !termination_message_sent_)
-    SharedWorkerDevToolsManager::GetInstance()->WorkerDestroyed(this);
 }
 
 void SharedWorkerHost::Start(
@@ -91,7 +114,7 @@ void SharedWorkerHost::Start(
   // Register with DevTools.
   bool pause_on_start;
   base::UnguessableToken devtools_worker_token;
-  SharedWorkerDevToolsManager::GetInstance()->WorkerCreated(
+  devtools_handle_ = std::make_unique<ScopedDevToolsHandle>(
       this, &pause_on_start, &devtools_worker_token);
 
   // Set up content settings interface.
@@ -152,8 +175,7 @@ void SharedWorkerHost::TerminateWorker() {
   if (termination_message_sent_)
     return;
   termination_message_sent_ = true;
-  if (!closed_)
-    SharedWorkerDevToolsManager::GetInstance()->WorkerDestroyed(this);
+  devtools_handle_.reset();
   worker_->Terminate();
   // Now, we wait to observe OnWorkerConnectionLost.
 }
@@ -186,13 +208,12 @@ void SharedWorkerHost::OnContextClosed() {
   // being sent to the worker (messages can still be sent from the worker,
   // for exception reporting, etc).
   closed_ = true;
-  if (!termination_message_sent_)
-    SharedWorkerDevToolsManager::GetInstance()->WorkerDestroyed(this);
+  devtools_handle_.reset();
 }
 
 void SharedWorkerHost::OnReadyForInspection() {
-  if (!closed_ && !termination_message_sent_)
-    SharedWorkerDevToolsManager::GetInstance()->WorkerReadyForInspection(this);
+  if (devtools_handle_)
+    devtools_handle_->WorkerReadyForInspection();
 }
 
 void SharedWorkerHost::OnScriptLoaded() {

content/browser/shared_worker/shared_worker_host.h

@@ -88,6 +88,7 @@ class SharedWorkerHost : public mojom::SharedWorkerHost,
   bool IsAvailable() const;
 
  private:
+  class ScopedDevToolsHandle;
   struct ClientInfo {
     ClientInfo(mojom::SharedWorkerClientPtr client,
                int connection_request_id,
@@ -135,6 +136,7 @@ class SharedWorkerHost : public mojom::SharedWorkerHost,
   bool termination_message_sent_ = false;
   bool closed_ = false;
   const base::TimeTicks creation_time_;
+  std::unique_ptr<ScopedDevToolsHandle> devtools_handle_;
 
   // This is the set of features that this worker has used.
   std::set<blink::mojom::WebFeature> used_features_;