Index: base/system_monitor/system_monitor_win.cc
===================================================================
--- base/system_monitor/system_monitor_win.cc	(revision 202711)
+++ base/system_monitor/system_monitor_win.cc	(working copy)
@@ -27,6 +27,14 @@
 
 SystemMonitor::PowerMessageWindow::PowerMessageWindow()
     : instance_(NULL), message_hwnd_(NULL) {
+  if (MessageLoop::current()->type() != MessageLoop::TYPE_UI) {
+    // Creating this window in (e.g.) a renderer inhibits shutdown on Windows.
+    // See http://crbug.com/230122. TODO(vandebo): http://crbug.com/236031
+    DLOG(ERROR)
+        << "Cannot create windows on non-UI thread, power monitor disabled!";
+    return;
+  }
+
   WNDCLASSEX window_class;
   base::win::InitializeWindowClass(
       kWindowClassName,
Index: content/renderer/renderer_main_platform_delegate_win.cc
===================================================================
--- content/renderer/renderer_main_platform_delegate_win.cc	(revision 202711)
+++ content/renderer/renderer_main_platform_delegate_win.cc	(working copy)
@@ -47,6 +47,14 @@
   base::win::SetAbortBehaviorForCrashReporting();
 }
 
+#if !defined(NDEBUG)
+LRESULT CALLBACK WindowsHookCBT(int code, WPARAM w_param, LPARAM l_param) {
+  CHECK_NE(code, HCBT_CREATEWND)
+      << "Should not be creating windows in the renderer!";
+  return CallNextHookEx(NULL, code, w_param, l_param);
+}
+#endif  // !NDEBUG
+
 }  // namespace
 
 RendererMainPlatformDelegate::RendererMainPlatformDelegate(
@@ -59,6 +67,15 @@
 }
 
 void RendererMainPlatformDelegate::PlatformInitialize() {
+#if !defined(NDEBUG)
+  // Install a check that we're not creating windows in the renderer. See
+  // http://crbug.com/230122 for background. TODO(scottmg): Ideally this would
+  // check all threads in the renderer, but it currently only checks the main
+  // thread.
+  PCHECK(
+      SetWindowsHookEx(WH_CBT, WindowsHookCBT, NULL, ::GetCurrentThreadId()));
+#endif  // !NDEBUG
+
   InitExitInterceptions();
 
   // Be mindful of what resources you acquire here. They can be used by
Index: ui/base/win/singleton_hwnd.cc
===================================================================
--- ui/base/win/singleton_hwnd.cc	(revision 202711)
+++ ui/base/win/singleton_hwnd.cc	(working copy)
@@ -5,6 +5,7 @@
 #include "ui/base/win/singleton_hwnd.h"
 
 #include "base/memory/singleton.h"
+#include "base/message_loop.h"
 
 namespace ui {
 
@@ -14,12 +15,22 @@
 }
 
 void SingletonHwnd::AddObserver(Observer* observer) {
-  if (!hwnd())
+  if (!hwnd()) {
+    if (!MessageLoop::current() ||
+        MessageLoop::current()->type() != MessageLoop::TYPE_UI) {
+      // Creating this window in (e.g.) a renderer inhibits shutdown on
+      // Windows. See http://crbug.com/230122 and http://crbug.com/236039.
+      DLOG(ERROR) << "Cannot create windows on non-UI thread!";
+      return;
+    }
     WindowImpl::Init(NULL, gfx::Rect());
+  }
   observer_list_.AddObserver(observer);
 }
 
 void SingletonHwnd::RemoveObserver(Observer* observer) {
+  if (!hwnd())
+    return;
   observer_list_.RemoveObserver(observer);
 }