Windows: Fix DCHECKs during shutdown with multi-threaded message loop mode (issue #2362)

libcef/common/main_delegate.cc

@@ -13,6 +13,7 @@
 #include "libcef/renderer/content_renderer_client.h"
 #include "libcef/utility/content_utility_client.h"
 
+#include "base/at_exit.h"
 #include "base/base_switches.h"
 #include "base/command_line.h"
 #include "base/files/file_path.h"
@@ -267,6 +268,14 @@ class CefUIThread : public base::Thread {
     browser_runner_->Shutdown();
     browser_runner_.reset(NULL);
 
+    // Release MessagePump resources registered with the AtExitManager.
+    base::MessageLoop* ml = const_cast<base::MessageLoop*>(message_loop());
+    base::MessageLoopCurrent::UnbindFromCurrentThreadInternal(ml);
+    ml->ReleasePump();
+
+    // Run exit callbacks on the UI thread to avoid sequence check failures.
+    base::AtExitManager::ProcessCallbacksNow();
+
 #if defined(OS_WIN)
     // Closes the COM library on the current thread. CoInitialize must
     // be balanced by a corresponding call to CoUninitialize.
@@ -642,13 +651,14 @@ void CefMainDelegate::ShutdownBrowser() {
     browser_runner_->Shutdown();
     browser_runner_.reset(NULL);
   }
+
+  message_loop_.reset();
+
   if (ui_thread_.get()) {
     // Blocks until the thread has stopped.
     ui_thread_->Stop();
     ui_thread_.reset();
   }
-
-  message_loop_.reset();
 }
 
 void CefMainDelegate::InitializeResourceBundle() {

patch/patch.cfg

@@ -52,6 +52,10 @@ patches = [
     #
     # Revert change that removes MessageLoopForUI constructor.
     # https://chromium-review.googlesource.com/751322
+    #
+    # Add MessageLoop::ReleasePump to fix crashes during shutdown with multi-
+    # threaded message loop mode.
+    # https://bitbucket.org/chromiumembedded/cef/issues/2362
     'name': 'message_loop',
   },
   {

patch/patches/message_loop.patch

@@ -13,10 +13,20 @@ index 3723960a5c0c..fa924f020f4e 100644
  MessageLoopCurrentForUI MessageLoopForUI::current() {
    return MessageLoopCurrentForUI::Get();
 diff --git base/message_loop/message_loop.h base/message_loop/message_loop.h
-index 7c31a128b53d..8d9dfdbc2a68 100644
+index 7c31a128b53d..7549d388cccb 100644
 --- base/message_loop/message_loop.h
 +++ base/message_loop/message_loop.h
-@@ -351,6 +351,7 @@ class BASE_EXPORT MessageLoop : public MessagePump::Delegate,
+@@ -195,6 +195,9 @@ class BASE_EXPORT MessageLoop : public MessagePump::Delegate,
+   // Runs the specified PendingTask.
+   void RunTask(PendingTask* pending_task);
+ 
++  // Called from Thread::CleanUp() to release resources.
++  void ReleasePump() { pump_ = nullptr; }
++
+   //----------------------------------------------------------------------------
+  protected:
+   std::unique_ptr<MessagePump> pump_;
+@@ -351,6 +354,7 @@ class BASE_EXPORT MessageLoop : public MessagePump::Delegate,
  class BASE_EXPORT MessageLoopForUI : public MessageLoop {
   public:
    explicit MessageLoopForUI(Type type = TYPE_UI);
@@ -24,6 +34,19 @@ index 7c31a128b53d..8d9dfdbc2a68 100644
  
    // TODO(gab): Mass migrate callers to MessageLoopCurrentForUI::Get()/IsSet().
    static MessageLoopCurrentForUI current();
+diff --git base/message_loop/message_loop_current.cc base/message_loop/message_loop_current.cc
+index 4959b70e0676..fdffe799433f 100644
+--- base/message_loop/message_loop_current.cc
++++ base/message_loop/message_loop_current.cc
+@@ -43,6 +43,8 @@ void MessageLoopCurrent::AddDestructionObserver(
+ 
+ void MessageLoopCurrent::RemoveDestructionObserver(
+     DestructionObserver* destruction_observer) {
++  if (!current_)
++    return;
+   DCHECK_CALLED_ON_VALID_THREAD(current_->bound_thread_checker_);
+   current_->destruction_observers_.RemoveObserver(destruction_observer);
+ }
 diff --git base/message_loop/message_loop_current.h base/message_loop/message_loop_current.h
 index 61d1607e31e7..656b3a9c9f68 100644
 --- base/message_loop/message_loop_current.h