Make session set in DevToolsAgentHost a vector

We want to maintain a deterministic order of agent enumeration.

Change-Id: Iac18573342cfb3cc6dbff305b0d64cfd00a13b78
Reviewed-on: https://chromium-review.googlesource.com/c/1287096Reviewed-by: Dmitry Gozman <dgozman@chromium.org>
Commit-Queue: Andrey Kosyakov <caseq@chromium.org>
Cr-Commit-Position: refs/heads/master@{#600803}

content/browser/devtools/devtools_agent_host_impl.cc

@@ -183,7 +183,7 @@ bool DevToolsAgentHostImpl::InnerAttachClient(DevToolsAgentHostClient* client,
   if (!AttachSession(session.get(), registry))
     return false;
   renderer_channel_.AttachSession(session.get());
-  sessions_.insert(session.get());
+  sessions_.push_back(session.get());
   session_by_client_[client] = std::move(session);
   if (sessions_.size() == 1)
     NotifyAttached();
@@ -240,7 +240,8 @@ void DevToolsAgentHostImpl::InnerDetachClient(DevToolsAgentHostClient* client) {
       std::move(session_by_client_[client]);
   // Make sure we dispose session prior to reporting it to the host.
   session->Dispose();
-  sessions_.erase(session.get());
+  sessions_.erase(
+      std::remove(sessions_.begin(), sessions_.end(), session.get()));
   session_by_client_.erase(client);
   DetachSession(session.get());
   DevToolsManager* manager = DevToolsManager::GetInstance();

content/browser/devtools/devtools_agent_host_impl.h

@@ -97,7 +97,7 @@ class CONTENT_EXPORT DevToolsAgentHostImpl : public DevToolsAgentHost {
   DevToolsIOContext* GetIOContext() { return &io_context_; }
   DevToolsRendererChannel* GetRendererChannel() { return &renderer_channel_; }
 
-  base::flat_set<DevToolsSession*>& sessions() { return sessions_; }
+  const std::vector<DevToolsSession*>& sessions() const { return sessions_; }
 
  private:
   friend class DevToolsAgentHost;  // for static methods
@@ -117,7 +117,7 @@ class CONTENT_EXPORT DevToolsAgentHostImpl : public DevToolsAgentHost {
                              TargetRegistry* registry);
 
   const std::string id_;
-  base::flat_set<DevToolsSession*> sessions_;
+  std::vector<DevToolsSession*> sessions_;
   base::flat_map<DevToolsAgentHostClient*, std::unique_ptr<DevToolsSession>>
       session_by_client_;
   DevToolsIOContext io_context_;