[Extensions] Chromium crashed in single-process mode on fresh launch.

With current implementation, in-process utility thread clean up is taken care by IO thread on detecting that concern IPC communication channel been closed. And utility thread has ThreadRestrictions to disallowed IO. Apparently it asserts (SIG-ABORT) before performing join in pre-check.

With this CL we are making sure that before IO thread waits for utility thread's cleanup it enables ThreadRestrictions to allow IO for utility thread so that it can join. This avoids chromium crash on fresh launch.

BUG=421007
R=mpcomplete@chromium.org

Review URL: https://codereview.chromium.org/683083002

Cr-Commit-Position: refs/heads/master@{#302112}

content/utility/in_process_utility_thread.cc

@@ -18,7 +18,10 @@ InProcessUtilityThread::InProcessUtilityThread(const std::string& channel_id)
 }
 
 InProcessUtilityThread::~InProcessUtilityThread() {
+  // Wait till in-process utility thread finishes clean up.
+  bool previous_value = base::ThreadRestrictions::SetIOAllowed(true);
   Stop();
+  base::ThreadRestrictions::SetIOAllowed(previous_value);
 }
 
 void InProcessUtilityThread::Init() {