Fix HostResolver crash when MessageLoop is destroyed during

net/base/host_resolver.cc

Index: net/base/host_resolver.cc
===================================================================
--- net/base/host_resolver.cc	(revision 9316)
+++ net/base/host_resolver.cc	(working copy)
@@ -63,8 +63,9 @@
 
 //-----------------------------------------------------------------------------
 
-class HostResolver::Request :
-    public base::RefCountedThreadSafe<HostResolver::Request> {
+class HostResolver::Request
+    : public base::RefCountedThreadSafe<HostResolver::Request>,
+      public MessageLoop::DestructionObserver {
  public:
   Request(HostResolver* resolver,
           const std::string& host,
@@ -80,9 +81,10 @@
         host_mapper_(host_mapper),
         error_(OK),
         results_(NULL) {
+    MessageLoop::current()->AddDestructionObserver(this);
   }
 
-  ~Request() {
+  virtual ~Request() {
     if (results_)
       freeaddrinfo(results_);
   }
@@ -111,6 +113,12 @@
     // Running on the origin thread.
     DCHECK(error_ || results_);
 
+    {
+      AutoLock locked(origin_loop_lock_);
+      if (origin_loop_)
+        origin_loop_->RemoveDestructionObserver(this);
+    }
+
     // We may have been cancelled!
     if (!resolver_)
       return;
@@ -135,6 +143,11 @@
     origin_loop_ = NULL;
   }
 
+  virtual void WillDestroyCurrentMessageLoop() {
+    AutoLock locked(origin_loop_lock_);
+    origin_loop_ = NULL;
+  }
+
  private:
   // Set on the origin thread, read on the worker thread.
   std::string host_;
@@ -169,8 +182,10 @@
 }
 
 HostResolver::~HostResolver() {
-  if (request_)
+  if (request_) {
     request_->Cancel();
+    MessageLoop::current()->RemoveDestructionObserver(request_.get());
+  }
 }
 
 int HostResolver::Resolve(const std::string& hostname, int port,
@@ -195,6 +210,7 @@
   if (!WorkerPool::PostTask(FROM_HERE,
           NewRunnableMethod(request_.get(), &Request::DoLookup), true)) {
     NOTREACHED();
+    MessageLoop::current()->RemoveDestructionObserver(request_.get());
     request_ = NULL;
     return ERR_FAILED;
   }