[DevTools] Support multiple sessions in Target domain

BUG=590878

Change-Id: Idcebf0336623322813b4cdfac66183d37c28f2bd
Reviewed-on: https://chromium-review.googlesource.com/573411
Commit-Queue: Dmitry Gozman <dgozman@chromium.org>
Reviewed-by: Andrey Kosyakov <caseq@chromium.org>
Cr-Commit-Position: refs/heads/master@{#488395}

content/browser/devtools/devtools_agent_host_impl.cc

@@ -186,6 +186,10 @@ void DevToolsAgentHostImpl::ForceAttachClient(DevToolsAgentHostClient* client) {
   InnerAttachClient(client);
 }
 
+void DevToolsAgentHostImpl::AttachMultiClient(DevToolsAgentHostClient* client) {
+  InnerAttachClient(client);
+}
+
 bool DevToolsAgentHostImpl::DetachClient(DevToolsAgentHostClient* client) {
   if (!SessionByClient(client))
     return false;

content/browser/devtools/devtools_agent_host_impl.h

@@ -44,6 +44,7 @@ class CONTENT_EXPORT DevToolsAgentHostImpl : public DevToolsAgentHost {
   void DisconnectWebContents() override;
   void ConnectWebContents(WebContents* wc) override;
 
+  void AttachMultiClient(DevToolsAgentHostClient* client);
   bool Inspect();
 
  protected:

content/browser/devtools/protocol/devtools_protocol_browsertest.cc

@@ -1657,6 +1657,8 @@ IN_PROC_BROWSER_TEST_F(DevToolsProtocolTest, TargetDiscovery) {
   EXPECT_TRUE(params->GetBoolean("targetInfo.attached", &is_attached));
   EXPECT_TRUE(is_attached);
   params = WaitForNotification("Target.attachedToTarget", true);
+  std::string session_id;
+  EXPECT_TRUE(params->GetString("sessionId", &session_id));
   EXPECT_TRUE(params->GetString("targetInfo.targetId", &temp));
   EXPECT_EQ(attached_id, temp);
   EXPECT_TRUE(notifications_.empty());
@@ -1667,9 +1669,11 @@ IN_PROC_BROWSER_TEST_F(DevToolsProtocolTest, TargetDiscovery) {
   EXPECT_TRUE(notifications_.empty());
 
   command_params.reset(new base::DictionaryValue());
-  command_params->SetString("targetId", attached_id);
+  command_params->SetString("sessionId", session_id);
   SendCommand("Target.detachFromTarget", std::move(command_params), true);
   params = WaitForNotification("Target.detachedFromTarget", true);
+  EXPECT_TRUE(params->GetString("sessionId", &temp));
+  EXPECT_EQ(session_id, temp);
   EXPECT_TRUE(params->GetString("targetId", &temp));
   EXPECT_EQ(attached_id, temp);
   EXPECT_TRUE(notifications_.empty());
@@ -1737,6 +1741,8 @@ IN_PROC_BROWSER_TEST_F(SitePerProcessDevToolsProtocolTest, TargetNoDiscovery) {
   command_params->SetBoolean("value", true);
   SendCommand("Target.setAttachToFrames", std::move(command_params), false);
   params = WaitForNotification("Target.attachedToTarget", true);
+  std::string session_id;
+  EXPECT_TRUE(params->GetString("sessionId", &session_id));
   EXPECT_TRUE(params->GetString("targetInfo.targetId", &target_id));
   EXPECT_TRUE(params->GetString("targetInfo.type", &temp));
   EXPECT_EQ("iframe", temp);
@@ -1748,10 +1754,13 @@ IN_PROC_BROWSER_TEST_F(SitePerProcessDevToolsProtocolTest, TargetNoDiscovery) {
   params = WaitForNotification("Target.detachedFromTarget", true);
   EXPECT_TRUE(params->GetString("targetId", &temp));
   EXPECT_EQ(target_id, temp);
+  EXPECT_TRUE(params->GetString("sessionId", &temp));
+  EXPECT_EQ(session_id, temp);
 
   // Navigate back to cross-site iframe.
   NavigateFrameToURL(root->child_at(0), cross_site_url);
   params = WaitForNotification("Target.attachedToTarget", true);
+  EXPECT_TRUE(params->GetString("sessionId", &session_id));
   EXPECT_TRUE(params->GetString("targetInfo.targetId", &target_id));
   EXPECT_TRUE(params->GetString("targetInfo.type", &temp));
   EXPECT_EQ("iframe", temp);
@@ -1764,6 +1773,8 @@ IN_PROC_BROWSER_TEST_F(SitePerProcessDevToolsProtocolTest, TargetNoDiscovery) {
   params = WaitForNotification("Target.detachedFromTarget", true);
   EXPECT_TRUE(params->GetString("targetId", &temp));
   EXPECT_EQ(target_id, temp);
+  EXPECT_TRUE(params->GetString("sessionId", &temp));
+  EXPECT_EQ(session_id, temp);
 }
 
 IN_PROC_BROWSER_TEST_F(DevToolsProtocolTest, SetAndGetCookies) {

content/browser/devtools/protocol/target_auto_attacher.cc

@@ -176,8 +176,8 @@ void TargetAutoAttacher::ReattachTargetsOfType(const Hosts& new_hosts,
   for (auto& it : new_hosts) {
     DevToolsAgentHost* host = it.get();
     if (old_hosts.find(host) == old_hosts.end()) {
-      if (attach_callback_.Run(host, waiting_for_debugger))
-        auto_attached_hosts_.insert(host);
+      attach_callback_.Run(host, waiting_for_debugger);
+      auto_attached_hosts_.insert(host);
     }
   }
 }

content/browser/devtools/protocol/target_auto_attacher.h

@@ -18,7 +18,7 @@ namespace protocol {
 class TargetAutoAttacher : public ServiceWorkerDevToolsManager::Observer {
  public:
   // Second parameter is |waiting_for_debugger|, returns whether it succeeded.
-  using AttachCallback = base::Callback<bool(DevToolsAgentHost*, bool)>;
+  using AttachCallback = base::Callback<void(DevToolsAgentHost*, bool)>;
   using DetachCallback = base::Callback<void(DevToolsAgentHost*)>;
 
   TargetAutoAttacher(AttachCallback attach_callback,

content/browser/devtools/protocol/target_handler.h

@@ -11,7 +11,6 @@
 #include "content/browser/devtools/protocol/devtools_domain_handler.h"
 #include "content/browser/devtools/protocol/target.h"
 #include "content/browser/devtools/protocol/target_auto_attacher.h"
-#include "content/public/browser/devtools_agent_host_client.h"
 #include "content/public/browser/devtools_agent_host_observer.h"
 
 namespace content {
@@ -23,7 +22,6 @@ namespace protocol {
 
 class TargetHandler : public DevToolsDomainHandler,
                       public Target::Backend,
-                      public DevToolsAgentHostClient,
                       public DevToolsAgentHostObserver {
  public:
   TargetHandler();
@@ -46,10 +44,12 @@ class TargetHandler : public DevToolsDomainHandler,
   Response SetRemoteLocations(
       std::unique_ptr<protocol::Array<Target::RemoteLocation>>) override;
   Response AttachToTarget(const std::string& target_id,
-                          bool* out_success) override;
-  Response DetachFromTarget(const std::string& target_id) override;
-  Response SendMessageToTarget(const std::string& target_id,
-                               const std::string& message) override;
+                          std::string* out_session_id) override;
+  Response DetachFromTarget(Maybe<std::string> session_id,
+                            Maybe<std::string> target_id) override;
+  Response SendMessageToTarget(const std::string& message,
+                               Maybe<std::string> session_id,
+                               Maybe<std::string> target_id) override;
   Response GetTargetInfo(
       const std::string& target_id,
       std::unique_ptr<Target::TargetInfo>* target_info) override;
@@ -69,14 +69,14 @@ class TargetHandler : public DevToolsDomainHandler,
       override;
 
  private:
-  using RawHostsMap = std::map<std::string, DevToolsAgentHost*>;
+  class Session;
 
-  void TargetCreatedInternal(DevToolsAgentHost* host);
-  void TargetInfoChangedInternal(DevToolsAgentHost* host);
-  void TargetDestroyedInternal(DevToolsAgentHost* host);
-  bool AttachToTargetInternal(DevToolsAgentHost* host,
-                              bool waiting_for_debugger);
-  void DetachFromTargetInternal(DevToolsAgentHost* host);
+  void AutoAttach(DevToolsAgentHost* host, bool waiting_for_debugger);
+  void AutoDetach(DevToolsAgentHost* host);
+  Response FindSession(Maybe<std::string> session_id,
+                       Maybe<std::string> target_id,
+                       Session** session,
+                       bool fall_through);
 
   // DevToolsAgentHostObserver implementation.
   bool ShouldForceDevToolsAgentHostCreation() override;
@@ -85,17 +85,13 @@ class TargetHandler : public DevToolsDomainHandler,
   void DevToolsAgentHostAttached(DevToolsAgentHost* agent_host) override;
   void DevToolsAgentHostDetached(DevToolsAgentHost* agent_host) override;
 
-  // DevToolsAgentHostClient implementation.
-  void DispatchProtocolMessage(DevToolsAgentHost* agent_host,
-                               const std::string& message) override;
-  void AgentHostClosed(DevToolsAgentHost* agent_host,
-                       bool replaced_with_another_client) override;
-
   std::unique_ptr<Target::Frontend> frontend_;
   TargetAutoAttacher auto_attacher_;
   bool discover_;
-  std::map<std::string, scoped_refptr<DevToolsAgentHost>> attached_hosts_;
-  RawHostsMap reported_hosts_;
+  std::map<std::string, std::unique_ptr<Session>> attached_sessions_;
+  std::map<DevToolsAgentHost*, Session*> auto_attached_sessions_;
+  std::set<DevToolsAgentHost*> reported_hosts_;
+  int last_session_id_ = 0;
 
   DISALLOW_COPY_AND_ASSIGN(TargetHandler);
 };

third_party/WebKit/LayoutTests/http/tests/inspector-protocol/resources/inspector-protocol-test.js

@@ -184,9 +184,9 @@ TestRunner.Page = class {
   }
 
   async createSession() {
-    await DevToolsAPI._sendCommandOrDie('Target.attachToTarget', {targetId: this._targetId});
-    var session = new TestRunner.Session(this);
-    DevToolsAPI._sessions.set(this._targetId, session);
+    var sessionId = (await DevToolsAPI._sendCommandOrDie('Target.attachToTarget', {targetId: this._targetId})).sessionId;
+    var session = new TestRunner.Session(this, sessionId);
+    DevToolsAPI._sessions.set(sessionId, session);
     return session;
   }
 
@@ -195,18 +195,12 @@ TestRunner.Page = class {
   }
 
   async _navigate(url) {
-    if (DevToolsAPI._sessions.get(this._targetId))
-      this._testRunner.die(`Cannot navigate to ${url} with active session`, new Error());
-
     var session = await this.createSession();
     await session._navigate(url);
     await session.disconnect();
   }
 
   async loadHTML(html) {
-    if (DevToolsAPI._sessions.get(this._targetId))
-      this._testRunner.die('Cannot loadHTML with active session', new Error());
-
     html = html.replace(/'/g, "\\'").replace(/\n/g, '\\n');
     var session = await this.createSession();
     await session.protocol.Runtime.evaluate({expression: `document.write('${html}');document.close();`});
@@ -215,9 +209,10 @@ TestRunner.Page = class {
 };
 
 TestRunner.Session = class {
-  constructor(page) {
+  constructor(page, sessionId) {
     this._testRunner = page._testRunner;
     this._page = page;
+    this._sessionId = sessionId;
     this._requestId = 0;
     this._dispatchTable = new Map();
     this._eventHandlers = new Map();
@@ -225,12 +220,12 @@ TestRunner.Session = class {
   }
 
   async disconnect() {
-    await DevToolsAPI._sendCommandOrDie('Target.detachFromTarget', {targetId: this._page._targetId});
+    await DevToolsAPI._sendCommandOrDie('Target.detachFromTarget', {sessionId: this._sessionId});
     DevToolsAPI._sessions.delete(this._page._targetId);
   }
 
   sendRawCommand(requestId, message) {
-    DevToolsAPI._sendCommandOrDie('Target.sendMessageToTarget', {targetId: this._page._targetId, message: message});
+    DevToolsAPI._sendCommandOrDie('Target.sendMessageToTarget', {sessionId: this._sessionId, message: message});
     return new Promise(f => this._dispatchTable.set(requestId, f));
   }
 
@@ -394,9 +389,9 @@ DevToolsAPI.dispatchMessage = function(messageOrObject) {
     } else {
       var eventName = messageObject.method;
       if (eventName === 'Target.receivedMessageFromTarget') {
-        var targetId = messageObject.params.targetId;
+        var sessionId = messageObject.params.sessionId;
         var message = messageObject.params.message;
-        var session = DevToolsAPI._sessions.get(targetId);
+        var session = DevToolsAPI._sessions.get(sessionId);
         if (session)
           session._dispatchMessage(JSON.parse(message));
       }

third_party/WebKit/LayoutTests/http/tests/inspector/service-workers/service-worker-agents-expected.txt

@@ -4,18 +4,18 @@ Debugger-related command should be issued: {
     "id": "<id>",
     "method": "Target.sendMessageToTarget",
     "params": {
-        "targetId": "<id>",
         "message": {
             "id": "<id>",
             "method": "Target.sendMessageToTarget",
             "params": {
-                "targetId": "<id>",
                 "message": {
                     "id": "<id>",
                     "method": "Debugger.enable"
-                }
+                },
+                "sessionId": "<id>"
             }
-        }
+        },
+        "sessionId": "<id>"
     }
 }
 Suspending targets.
@@ -24,18 +24,18 @@ Debugger-related command should be issued: {
     "id": "<id>",
     "method": "Target.sendMessageToTarget",
     "params": {
-        "targetId": "<id>",
         "message": {
             "id": "<id>",
             "method": "Target.sendMessageToTarget",
             "params": {
-                "targetId": "<id>",
                 "message": {
                     "id": "<id>",
                     "method": "Debugger.enable"
-                }
+                },
+                "sessionId": "<id>"
             }
-        }
+        },
+        "sessionId": "<id>"
     }
 }
 

third_party/WebKit/Source/core/inspector/InspectorWorkerAgent.cpp

@@ -38,18 +38,16 @@
 
 namespace blink {
 
+using protocol::Maybe;
 using protocol::Response;
 
 namespace WorkerAgentState {
 static const char kAutoAttach[] = "autoAttach";
 static const char kWaitForDebuggerOnStart[] = "waitForDebuggerOnStart";
-static const char kAttachedWorkerIds[] = "attachedWorkerIds";
+static const char kAttachedSessionIds[] = "attachedSessionIds";
 };
 
-namespace {
-// TODO(dgozman): support multiple sessions in protocol.
-static const int kSessionId = 1;
-}  // namespace
+int InspectorWorkerAgent::s_last_connection_ = 0;
 
 InspectorWorkerAgent::InspectorWorkerAgent(InspectedFrames* inspected_frames)
     : inspected_frames_(inspected_frames) {}
@@ -60,10 +58,10 @@ void InspectorWorkerAgent::Restore() {
   if (!AutoAttachEnabled())
     return;
   instrumenting_agents_->addInspectorWorkerAgent(this);
-  protocol::DictionaryValue* attached = AttachedWorkerIds();
+  protocol::DictionaryValue* attached = AttachedSessionIds();
   for (size_t i = 0; i < attached->size(); ++i)
     GetFrontend()->detachedFromTarget(attached->at(i).first);
-  state_->remove(WorkerAgentState::kAttachedWorkerIds);
+  state_->remove(WorkerAgentState::kAttachedSessionIds);
   ConnectToAllProxies();
 }
 
@@ -74,7 +72,7 @@ Response InspectorWorkerAgent::disable() {
   }
   state_->setBoolean(WorkerAgentState::kAutoAttach, false);
   state_->setBoolean(WorkerAgentState::kWaitForDebuggerOnStart, false);
-  state_->remove(WorkerAgentState::kAttachedWorkerIds);
+  state_->remove(WorkerAgentState::kAttachedSessionIds);
   return Response::OK();
 }
 
@@ -104,13 +102,33 @@ bool InspectorWorkerAgent::AutoAttachEnabled() {
   return state_->booleanProperty(WorkerAgentState::kAutoAttach, false);
 }
 
-Response InspectorWorkerAgent::sendMessageToTarget(const String& target_id,
-                                                   const String& message) {
-  WorkerInspectorProxy* proxy = connected_proxies_.at(target_id);
-  if (!proxy)
-    return Response::Error("Not attached to a target with given id");
-  proxy->SendMessageToInspector(kSessionId, message);
-  return Response::OK();
+Response InspectorWorkerAgent::sendMessageToTarget(const String& message,
+                                                   Maybe<String> session_id,
+                                                   Maybe<String> target_id) {
+  if (session_id.isJust()) {
+    auto it = session_id_to_connection_.find(session_id.fromJust());
+    if (it == session_id_to_connection_.end())
+      return Response::Error("No session with given id");
+    WorkerInspectorProxy* proxy = connected_proxies_.at(it->value);
+    proxy->SendMessageToInspector(it->value, message);
+    return Response::OK();
+  }
+  if (target_id.isJust()) {
+    int connection = 0;
+    for (auto& it : connected_proxies_) {
+      if (it.value->InspectorId() == target_id.fromJust()) {
+        if (connection)
+          return Response::Error("Multiple sessions attached, specify id");
+        connection = it.key;
+      }
+    }
+    if (!connection)
+      return Response::Error("No target with given id");
+    WorkerInspectorProxy* proxy = connected_proxies_.at(connection);
+    proxy->SendMessageToInspector(connection, message);
+    return Response::OK();
+  }
+  return Response::Error("Session id must be specified");
 }
 
 void InspectorWorkerAgent::SetTracingSessionId(
@@ -138,12 +156,20 @@ void InspectorWorkerAgent::DidStartWorker(WorkerInspectorProxy* proxy,
 
 void InspectorWorkerAgent::WorkerTerminated(WorkerInspectorProxy* proxy) {
   DCHECK(GetFrontend() && AutoAttachEnabled());
-  if (connected_proxies_.find(proxy->InspectorId()) == connected_proxies_.end())
-    return;
-  AttachedWorkerIds()->remove(proxy->InspectorId());
-  GetFrontend()->detachedFromTarget(proxy->InspectorId());
-  proxy->DisconnectFromInspector(kSessionId, this);
-  connected_proxies_.erase(proxy->InspectorId());
+  Vector<String> session_ids;
+  for (auto& it : session_id_to_connection_) {
+    if (connected_proxies_.at(it.value) == proxy)
+      session_ids.push_back(it.key);
+  }
+  for (const String& session_id : session_ids) {
+    AttachedSessionIds()->remove(session_id);
+    GetFrontend()->detachedFromTarget(session_id, proxy->InspectorId());
+    int connection = session_id_to_connection_.at(session_id);
+    proxy->DisconnectFromInspector(connection, this);
+    connected_proxies_.erase(connection);
+    connection_to_session_id_.erase(connection);
+    session_id_to_connection_.erase(session_id);
+  }
 }
 
 void InspectorWorkerAgent::ConnectToAllProxies() {
@@ -152,19 +178,23 @@ void InspectorWorkerAgent::ConnectToAllProxies() {
     DCHECK(proxy->GetExecutionContext()->IsDocument());
     Document* document = ToDocument(proxy->GetExecutionContext());
     if (document->GetFrame() &&
-        inspected_frames_->Contains(document->GetFrame()))
+        inspected_frames_->Contains(document->GetFrame())) {
       ConnectToProxy(proxy, false);
+    }
   }
 }
 
 void InspectorWorkerAgent::DisconnectFromAllProxies(bool report_to_frontend) {
-  for (auto& id_proxy : connected_proxies_) {
+  for (auto& it : session_id_to_connection_) {
+    WorkerInspectorProxy* proxy = connected_proxies_.at(it.value);
     if (report_to_frontend) {
-      AttachedWorkerIds()->remove(id_proxy.key);
-      GetFrontend()->detachedFromTarget(id_proxy.key);
+      AttachedSessionIds()->remove(it.key);
+      GetFrontend()->detachedFromTarget(it.key, proxy->InspectorId());
     }
-    id_proxy.value->DisconnectFromInspector(kSessionId, this);
+    proxy->DisconnectFromInspector(it.value, this);
   }
+  connection_to_session_id_.clear();
+  session_id_to_connection_.clear();
   connected_proxies_.clear();
 }
 
@@ -175,33 +205,36 @@ void InspectorWorkerAgent::DidCommitLoadForLocalFrame(LocalFrame* frame) {
   // During navigation workers from old page may die after a while.
   // Usually, it's fine to report them terminated later, but some tests
   // expect strict set of workers, and we reuse renderer between tests.
-  for (auto& id_proxy : connected_proxies_) {
-    AttachedWorkerIds()->remove(id_proxy.key);
-    GetFrontend()->detachedFromTarget(id_proxy.key);
-    id_proxy.value->DisconnectFromInspector(kSessionId, this);
-  }
-  connected_proxies_.clear();
+  DisconnectFromAllProxies(true);
 }
 
-protocol::DictionaryValue* InspectorWorkerAgent::AttachedWorkerIds() {
+protocol::DictionaryValue* InspectorWorkerAgent::AttachedSessionIds() {
   protocol::DictionaryValue* ids =
-      state_->getObject(WorkerAgentState::kAttachedWorkerIds);
+      state_->getObject(WorkerAgentState::kAttachedSessionIds);
   if (!ids) {
     std::unique_ptr<protocol::DictionaryValue> new_ids =
         protocol::DictionaryValue::create();
     ids = new_ids.get();
-    state_->setObject(WorkerAgentState::kAttachedWorkerIds, std::move(new_ids));
+    state_->setObject(WorkerAgentState::kAttachedSessionIds,
+                      std::move(new_ids));
   }
   return ids;
 }
 
 void InspectorWorkerAgent::ConnectToProxy(WorkerInspectorProxy* proxy,
                                           bool waiting_for_debugger) {
-  connected_proxies_.Set(proxy->InspectorId(), proxy);
-  proxy->ConnectToInspector(kSessionId, this);
+  int connection = ++s_last_connection_;
+  connected_proxies_.Set(connection, proxy);
+
+  String session_id = proxy->InspectorId() + "-" + String::Number(connection);
+  session_id_to_connection_.Set(session_id, connection);
+  connection_to_session_id_.Set(connection, session_id);
+
+  proxy->ConnectToInspector(connection, this);
   DCHECK(GetFrontend());
-  AttachedWorkerIds()->setBoolean(proxy->InspectorId(), true);
-  GetFrontend()->attachedToTarget(protocol::Target::TargetInfo::create()
+  AttachedSessionIds()->setBoolean(session_id, true);
+  GetFrontend()->attachedToTarget(session_id,
+                                  protocol::Target::TargetInfo::create()
                                       .setTargetId(proxy->InspectorId())
                                       .setType("worker")
                                       .setTitle(proxy->Url())
@@ -213,10 +246,13 @@ void InspectorWorkerAgent::ConnectToProxy(WorkerInspectorProxy* proxy,
 
 void InspectorWorkerAgent::DispatchMessageFromWorker(
     WorkerInspectorProxy* proxy,
-    int session_id,
+    int connection,
     const String& message) {
-  DCHECK(session_id == kSessionId);
-  GetFrontend()->receivedMessageFromTarget(proxy->InspectorId(), message);
+  auto it = connection_to_session_id_.find(connection);
+  if (it == connection_to_session_id_.end())
+    return;
+  GetFrontend()->receivedMessageFromTarget(it->value, message,
+                                           proxy->InspectorId());
 }
 
 DEFINE_TRACE(InspectorWorkerAgent) {

third_party/WebKit/Source/core/inspector/InspectorWorkerAgent.h

@@ -65,8 +65,10 @@ class CORE_EXPORT InspectorWorkerAgent final
   protocol::Response setAutoAttach(bool auto_attach,
                                    bool wait_for_debugger_on_start) override;
   protocol::Response setAttachToFrames(bool attach) override;
-  protocol::Response sendMessageToTarget(const String& target_id,
-                                         const String& message) override;
+  protocol::Response sendMessageToTarget(
+      const String& message,
+      protocol::Maybe<String> session_id,
+      protocol::Maybe<String> target_id) override;
 
   void SetTracingSessionId(const String&);
 
@@ -75,16 +77,19 @@ class CORE_EXPORT InspectorWorkerAgent final
   void ConnectToAllProxies();
   void DisconnectFromAllProxies(bool report_to_frontend);
   void ConnectToProxy(WorkerInspectorProxy*, bool waiting_for_debugger);
-  protocol::DictionaryValue* AttachedWorkerIds();
+  protocol::DictionaryValue* AttachedSessionIds();
 
   // WorkerInspectorProxy::PageInspector implementation.
   void DispatchMessageFromWorker(WorkerInspectorProxy*,
-                                 int session_id,
+                                 int connection,
                                  const String& message) override;
 
   Member<InspectedFrames> inspected_frames_;
-  HeapHashMap<String, Member<WorkerInspectorProxy>> connected_proxies_;
+  HeapHashMap<int, Member<WorkerInspectorProxy>> connected_proxies_;
+  HashMap<int, String> connection_to_session_id_;
+  HashMap<String, int> session_id_to_connection_;
   String tracing_session_id_;
+  static int s_last_connection_;
 };
 
 }  // namespace blink

third_party/WebKit/Source/core/inspector/browser_protocol.json

@@ -3601,6 +3601,11 @@
                 "id": "TargetID",
                 "type": "string"
             },
+            {
+                "id": "SessionID",
+                "type": "string",
+                "description": "Unique identifier of attached debugging session."
+            },
             {
                 "id": "BrowserContextID",
                 "type": "string"
@@ -3656,10 +3661,11 @@
             },
             {
                 "name": "sendMessageToTarget",
-                "description": "Sends protocol message to the target with given id.",
+                "description": "Sends protocol message over session with given id.",
                 "parameters": [
-                    { "name": "targetId", "$ref": "TargetID" },
-                    { "name": "message", "type": "string" }
+                    { "name": "message", "type": "string" },
+                    { "name": "sessionId", "$ref": "SessionID", "optional": true, "description": "Identifier of the session." },
+                    { "name": "targetId", "$ref": "TargetID", "optional": true, "deprecated": true, "description": "Deprecated." }
                 ]
             },
             {
@@ -3696,14 +3702,15 @@
                     { "name": "targetId", "$ref": "TargetID" }
                 ],
                 "returns": [
-                    { "name": "success", "type": "boolean", "description": "Whether attach succeeded." }
+                    { "name": "sessionId", "$ref": "SessionID", "description": "Id assigned to the session." }
                 ]
             },
             {
                 "name": "detachFromTarget",
-                "description": "Detaches from the target with given id.",
+                "description": "Detaches session with given id.",
                 "parameters": [
-                    { "name": "targetId", "$ref": "TargetID" }
+                    { "name": "sessionId", "$ref": "SessionID", "optional": true, "description": "Session to detach." },
+                    { "name": "targetId", "$ref": "TargetID", "optional": true, "deprecated": true, "description": "Deprecated." }
                 ]
             },
             {
@@ -3770,23 +3777,26 @@
                 "name": "attachedToTarget",
                 "description": "Issued when attached to target because of auto-attach or <code>attachToTarget</code> command.",
                 "parameters": [
+                    { "name": "sessionId", "$ref": "SessionID", "description": "Identifier assigned to the session used to send/receive messages." },
                     { "name": "targetInfo", "$ref": "TargetInfo" },
                     { "name": "waitingForDebugger", "type": "boolean" }
                 ]
             },
             {
                 "name": "detachedFromTarget",
-                "description": "Issued when detached from target for any reason (including <code>detachFromTarget</code> command).",
+                "description": "Issued when detached from target for any reason (including <code>detachFromTarget</code> command). Can be issued multiple times per target if multiple sessions have been attached to it.",
                 "parameters": [
-                    { "name": "targetId", "$ref": "TargetID" }
+                    { "name": "sessionId", "$ref": "SessionID", "description": "Detached session identifier." },
+                    { "name": "targetId", "$ref": "TargetID", "optional": true, "deprecated": true, "description": "Deprecated." }
                 ]
             },
             {
                 "name": "receivedMessageFromTarget",
-                "description": "Notifies about new protocol message from attached target.",
+                "description": "Notifies about a new protocol message received from the session (as reported in <code>attachedToTarget</code> event).",
                 "parameters": [
-                    { "name": "targetId", "$ref": "TargetID" },
-                    { "name": "message", "type": "string" }
+                    { "name": "sessionId", "$ref": "SessionID", "description": "Identifier of a session which sends a message." },
+                    { "name": "message", "type": "string" },
+                    { "name": "targetId", "$ref": "TargetID", "optional": true, "deprecated": true, "description": "Deprecated." }
                 ]
             }
         ]

third_party/WebKit/Source/devtools/front_end/sdk/TargetManager.js

@@ -457,10 +457,8 @@ SDK.ChildTargetManager = class {
           InspectorFrontendHostAPI.Events.DevicesDiscoveryConfigChanged, this._devicesDiscoveryConfigChanged, this);
     }
 
-    // TODO(dgozman): this is O(n^2) when removing main target.
-    var childTargets = this._targetManager._targets.filter(child => child.parentTarget() === this._parentTarget);
-    for (var child of childTargets)
-      this.detachedFromTarget(child.id());
+    for (var sessionId of this._childConnections.keys())
+      this.detachedFromTarget(sessionId, undefined);
   }
 
   /**
@@ -534,10 +532,11 @@ SDK.ChildTargetManager = class {
 
   /**
    * @override
+   * @param {string} sessionId
    * @param {!Protocol.Target.TargetInfo} targetInfo
    * @param {boolean} waitingForDebugger
    */
-  attachedToTarget(targetInfo, waitingForDebugger) {
+  attachedToTarget(sessionId, targetInfo, waitingForDebugger) {
     var targetName = '';
     if (targetInfo.type === 'node') {
       targetName = Common.UIString('Node.js: %s', targetInfo.url);
@@ -548,7 +547,7 @@ SDK.ChildTargetManager = class {
     }
     var target = this._targetManager.createTarget(
         targetInfo.targetId, targetName, this._capabilitiesForType(targetInfo.type),
-        this._createChildConnection.bind(this, this._targetAgent, targetInfo.targetId), this._parentTarget);
+        this._createChildConnection.bind(this, this._targetAgent, sessionId), this._parentTarget);
 
     // Only pause the new worker if debugging SW - we are going through the pause on start checkbox.
     if (!this._parentTarget.parentTarget() && Runtime.queryParam('isSharedWorker') && waitingForDebugger) {
@@ -564,33 +563,35 @@ SDK.ChildTargetManager = class {
 
   /**
    * @override
-   * @param {string} childTargetId
+   * @param {string} sessionId
+   * @param {string=} childTargetId
    */
-  detachedFromTarget(childTargetId) {
-    this._childConnections.get(childTargetId)._onDisconnect.call(null, 'target terminated');
-    this._childConnections.delete(childTargetId);
+  detachedFromTarget(sessionId, childTargetId) {
+    this._childConnections.get(sessionId)._onDisconnect.call(null, 'target terminated');
+    this._childConnections.delete(sessionId);
   }
 
   /**
    * @override
-   * @param {string} childTargetId
+   * @param {string} sessionId
    * @param {string} message
+   * @param {string=} childTargetId
    */
-  receivedMessageFromTarget(childTargetId, message) {
-    var connection = this._childConnections.get(childTargetId);
+  receivedMessageFromTarget(sessionId, message, childTargetId) {
+    var connection = this._childConnections.get(sessionId);
     if (connection)
       connection._onMessage.call(null, message);
   }
 
   /**
    * @param {!Protocol.TargetAgent} agent
-   * @param {string} childTargetId
+   * @param {string} sessionId
    * @param {!Protocol.InspectorBackend.Connection.Params} params
    * @return {!Protocol.InspectorBackend.Connection}
    */
-  _createChildConnection(agent, childTargetId, params) {
-    var connection = new SDK.ChildConnection(agent, childTargetId, params);
-    this._childConnections.set(childTargetId, connection);
+  _createChildConnection(agent, sessionId, params) {
+    var connection = new SDK.ChildConnection(agent, sessionId, params);
+    this._childConnections.set(sessionId, connection);
     return connection;
   }
 };
@@ -601,12 +602,12 @@ SDK.ChildTargetManager = class {
 SDK.ChildConnection = class {
   /**
    * @param {!Protocol.TargetAgent} agent
-   * @param {string} targetId
+   * @param {string} sessionId
    * @param {!Protocol.InspectorBackend.Connection.Params} params
    */
-  constructor(agent, targetId, params) {
+  constructor(agent, sessionId, params) {
     this._agent = agent;
-    this._targetId = targetId;
+    this._sessionId = sessionId;
     this._onMessage = params.onMessage;
     this._onDisconnect = params.onDisconnect;
   }
@@ -616,7 +617,7 @@ SDK.ChildConnection = class {
    * @param {string} message
    */
   sendMessage(message) {
-    this._agent.sendMessageToTarget(this._targetId, message);
+    this._agent.sendMessageToTarget(message, this._sessionId);
   }
 
   /**