[inspector] Support multiple sessions per context group

src/inspector/v8-debugger-agent-impl.cc

 // Copyright 2015 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/inspector/v8-debugger-agent-impl.h"
 
 #include <algorithm>
 
 #include "src/debug/debug-interface.h"
 #include "src/inspector/injected-script.h"
@@ skipping 1220 matching lines @@
   m_frontend.resumed();
 }
 
 void V8DebuggerAgentImpl::breakProgram(
     const String16& breakReason,
     std::unique_ptr<protocol::DictionaryValue> data) {
   if (!enabled() || !m_debugger->canBreakProgram() || m_skipAllPauses) return;
   std::vector<BreakReason> currentScheduledReason;
   currentScheduledReason.swap(m_breakReason);
   pushBreakDetails(breakReason, std::move(data));
-  if (!m_debugger->breakProgram(m_session->contextGroupId())) return;
+
+  int contextGroupId = m_session->contextGroupId();
+  int sessionId = m_session->sessionId();
+  V8InspectorImpl* inspector = m_inspector;
+  m_debugger->breakProgram(contextGroupId);
+  // Check that session and |this| are still around.
+  if (!inspector->sessionById(contextGroupId, sessionId)) return;
+  if (!enabled()) return;
+
   popBreakDetails();
   m_breakReason.swap(currentScheduledReason);
   if (!m_breakReason.empty()) {
     m_debugger->setPauseOnNextStatement(true, m_session->contextGroupId());
   }
 }
 
 void V8DebuggerAgentImpl::breakProgramOnException(
     const String16& breakReason,
     std::unique_ptr<protocol::DictionaryValue> data) {
@@ skipping 22 matching lines @@
 
 void V8DebuggerAgentImpl::reset() {
   if (!enabled()) return;
   m_blackboxedPositions.clear();
   resetBlackboxedStateCache();
   m_scripts.clear();
   m_breakpointIdToDebuggerBreakpointIds.clear();
 }
 
 }  // namespace v8_inspector