Query NaCl processes' GDB debug port on the correct thread.

chrome/browser/task_manager/sampling/task_group.cc

Index: chrome/browser/task_manager/sampling/task_group.cc
diff --git a/chrome/browser/task_manager/sampling/task_group.cc b/chrome/browser/task_manager/sampling/task_group.cc
index d7fab26f8d64944db4aa3da4f1b4d03a783e06c9..959770a005c7bd4a5413d4d97271a97de793272a 100644
--- a/chrome/browser/task_manager/sampling/task_group.cc
+++ b/chrome/browser/task_manager/sampling/task_group.cc
@@ -90,7 +90,7 @@ TaskGroup::TaskGroup(
       user_peak_handles_(-1),
 #endif  // defined(OS_WIN)
 #if !defined(DISABLE_NACL)
-      nacl_debug_stub_port_(-1),
+      nacl_debug_stub_port_(nacl::kGdbDebugStubPortUnknown),
 #endif  // !defined(DISABLE_NACL)
       idle_wakeups_per_second_(-1),
 #if defined(OS_LINUX)
@@ -258,12 +258,15 @@ void TaskGroup::RefreshWindowsHandles() {
 }
 
 #if !defined(DISABLE_NACL)
+static int GetNaClDebugStubPortOnIoThread(int process_id) {
+  return nacl::NaClBrowser::GetInstance()->GetProcessGdbDebugStubPort(
+      process_id);
+}
+
 void TaskGroup::RefreshNaClDebugStubPort(int child_process_unique_id) {
-  nacl::NaClBrowser* nacl_browser = nacl::NaClBrowser::GetInstance();
   content::BrowserThread::PostTaskAndReplyWithResult(
       content::BrowserThread::IO, FROM_HERE,
-      base::Bind(&nacl::NaClBrowser::GetProcessGdbDebugStubPort,
-                 base::Unretained(nacl_browser), child_process_unique_id),
+      base::Bind(&GetNaClDebugStubPortOnIoThread, child_process_unique_id),
       base::Bind(&TaskGroup::OnRefreshNaClDebugStubPortDone,
                  weak_ptr_factory_.GetWeakPtr()));
 }