[inspector] Support multiple sessions per context group

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

Index: src/inspector/v8-debugger-agent-impl.cc
diff --git a/src/inspector/v8-debugger-agent-impl.cc b/src/inspector/v8-debugger-agent-impl.cc
index 96c995aecf686bc85ced0b7551fbe508b9c141fd..0e073b81ca09a97ff9bc3f5e7075b7751c3efb76 100644
--- a/src/inspector/v8-debugger-agent-impl.cc
+++ b/src/inspector/v8-debugger-agent-impl.cc
@@ -1238,7 +1238,15 @@ void V8DebuggerAgentImpl::breakProgram(
   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()) {