Split UI thread shutdown into before and after stages (see #3609)

Existing UI thread shutdown tasks need to be executed before the UI
thread RunLoop is terminated. Those tasks have now been moved to
CefMainRunner::StartShutdownOnUIThread and FinishShutdownOnUIThread is
now called after the RunLoop is terminated.

This fixes a shutdown crash in ChromeProcessSingleton::DeleteInstance.
DeleteInstance needs to be called on the UI thread near the end of the
shutdown process (after ChromeProcessSingleton::Cleanup is called via
PostMainMessageLoopRun).

libcef/common/alloy/alloy_main_runner_delegate.cc

@@ -9,6 +9,7 @@
 #include "libcef/common/alloy/alloy_main_delegate.h"
 #include "libcef/renderer/alloy/alloy_content_renderer_client.h"
 
+#include "chrome/browser/chrome_process_singleton.h"
 #include "content/public/browser/render_process_host.h"
 #include "ui/base/resource/resource_bundle.h"
 
@@ -42,13 +43,17 @@ void AlloyMainRunnerDelegate::AfterUIThreadInitialize() {
       ->OnContextInitialized();
 }
 
-void AlloyMainRunnerDelegate::AfterUIThreadShutdown() {
+void AlloyMainRunnerDelegate::BeforeUIThreadShutdown() {
   static_cast<ChromeBrowserProcessAlloy*>(g_browser_process)
       ->CleanupOnUIThread();
 
   ui::ResourceBundle::GetSharedInstance().CleanupOnUIThread();
 }
 
+void AlloyMainRunnerDelegate::AfterUIThreadShutdown() {
+  ChromeProcessSingleton::DeleteInstance();
+}
+
 void AlloyMainRunnerDelegate::BeforeMainThreadShutdown() {
   if (content::RenderProcessHost::run_renderer_in_process()) {
     // Blocks until RenderProcess cleanup is complete.

libcef/common/alloy/alloy_main_runner_delegate.h

@@ -33,6 +33,7 @@ class AlloyMainRunnerDelegate : public CefMainRunnerDelegate {
   void BeforeMainThreadInitialize(const CefMainArgs& args) override;
   void BeforeMainThreadRun(bool multi_threaded_message_loop) override;
   void AfterUIThreadInitialize() override;
+  void BeforeUIThreadShutdown() override;
   void AfterUIThreadShutdown() override;
   void BeforeMainThreadShutdown() override;
   void AfterMainThreadShutdown() override;

libcef/common/chrome/chrome_main_runner_delegate.cc

@@ -12,6 +12,7 @@
 #include "base/run_loop.h"
 #include "chrome/browser/browser_process_impl.h"
 #include "chrome/browser/chrome_content_browser_client.h"
+#include "chrome/browser/chrome_process_singleton.h"
 #include "chrome/common/profiler/main_thread_stack_sampling_profiler.h"
 #include "components/keep_alive_registry/keep_alive_types.h"
 #include "components/keep_alive_registry/scoped_keep_alive.h"
@@ -46,6 +47,8 @@ void ChromeMainRunnerDelegate::BeforeMainThreadInitialize(
 void ChromeMainRunnerDelegate::BeforeMainThreadRun(
     bool multi_threaded_message_loop) {
   if (multi_threaded_message_loop) {
+    multi_threaded_message_loop_ = true;
+
     // Detach from the main thread so that these objects can be attached and
     // modified from the UI thread going forward.
     metrics::GlobalPersistentSystemProfile::GetInstance()
@@ -83,7 +86,7 @@ void ChromeMainRunnerDelegate::BeforeUIThreadInitialize() {
   sampling_profiler_ = std::make_unique<MainThreadStackSamplingProfiler>();
 }
 
-void ChromeMainRunnerDelegate::AfterUIThreadShutdown() {
+void ChromeMainRunnerDelegate::BeforeUIThreadShutdown() {
   static_cast<ChromeContentBrowserClient*>(
       CefAppManager::Get()->GetContentClient()->browser())
       ->CleanupOnUIThread();
@@ -92,6 +95,14 @@ void ChromeMainRunnerDelegate::AfterUIThreadShutdown() {
   sampling_profiler_.reset();
 }
 
+void ChromeMainRunnerDelegate::AfterUIThreadShutdown() {
+  if (multi_threaded_message_loop_) {
+    // Don't wait for this to be called in ChromeMainDelegate::ProcessExiting.
+    // It is safe to call multiple times.
+    ChromeProcessSingleton::DeleteInstance();
+  }
+}
+
 void ChromeMainRunnerDelegate::BeforeExecuteProcess(const CefMainArgs& args) {
   BeforeMainThreadInitialize(args);
 }

libcef/common/chrome/chrome_main_runner_delegate.h

@@ -37,6 +37,7 @@ class ChromeMainRunnerDelegate : public CefMainRunnerDelegate {
   void BeforeMainMessageLoopRun(base::RunLoop* run_loop) override;
   bool HandleMainMessageLoopQuit() override;
   void BeforeUIThreadInitialize() override;
+  void BeforeUIThreadShutdown() override;
   void AfterUIThreadShutdown() override;
   void BeforeExecuteProcess(const CefMainArgs& args) override;
   void AfterExecuteProcess() override;
@@ -50,6 +51,8 @@ class ChromeMainRunnerDelegate : public CefMainRunnerDelegate {
   CefMainRunnerHandler* const runner_;
   CefSettings* const settings_;
   CefRefPtr<CefApp> application_;
+
+  bool multi_threaded_message_loop_ = false;
 };
 
 #endif  // CEF_LIBCEF_COMMON_CHROME_CHROME_MAIN_RUNNER_DELEGATE_CEF_

libcef/common/main_runner_delegate.h

@@ -26,6 +26,7 @@ class CefMainRunnerDelegate {
   virtual bool HandleMainMessageLoopQuit() { return false; }
   virtual void BeforeUIThreadInitialize() {}
   virtual void AfterUIThreadInitialize() {}
+  virtual void BeforeUIThreadShutdown() {}
   virtual void AfterUIThreadShutdown() {}
   virtual void BeforeMainThreadShutdown() {}
   virtual void AfterMainThreadShutdown() {}