Attempt at fixing crash where compositor is null

It would appear we can end up getting a WM_PAINT when we have no
compositor. Seems like the only way for this to happen is if we get a
WM_DESTROY then a WM_PAINT. Seems suspicious...

BUG=361742
TEST=none
R=ben@chromium.org

Review URL: https://codereview.chromium.org/287563006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@270246 0039d316-1c4b-4281-b951-d872f2087c98

ui/views/widget/desktop_aura/desktop_window_tree_host_win.cc

@@ -864,7 +864,9 @@ bool DesktopWindowTreeHostWin::HandlePaintAccelerated(
 }
 
 void DesktopWindowTreeHostWin::HandlePaint(gfx::Canvas* canvas) {
-  compositor()->ScheduleRedrawRect(gfx::Rect());
+  // It appears possible to get WM_PAINT after WM_DESTROY.
+  if (compositor())
+    compositor()->ScheduleRedrawRect(gfx::Rect());
 }
 
 bool DesktopWindowTreeHostWin::HandleTooltipNotify(int w_param,

ui/views/win/hwnd_message_handler.cc

@@ -911,10 +911,9 @@ LRESULT HWNDMessageHandler::OnWndProc(UINT message,
   if (!::IsWindow(window))
     return result;
 
-  if (delegate_)
+  if (delegate_) {
     delegate_->PostHandleMSG(message, w_param, l_param);
-  if (message == WM_NCDESTROY) {
-    if (delegate_)
+    if (message == WM_NCDESTROY)
       delegate_->HandleDestroyed();
   }