Gets events dispatching working in mushrome

chrome/browser/ui/ash/ash_init.cc

Index: chrome/browser/ui/ash/ash_init.cc
diff --git a/chrome/browser/ui/ash/ash_init.cc b/chrome/browser/ui/ash/ash_init.cc
index a35819b601d0b5ac1f2c71e974a5a98ab731dc72..0368685cc25367fb43c93881485fb26dfe591cbc 100644
--- a/chrome/browser/ui/ash/ash_init.cc
+++ b/chrome/browser/ui/ash/ash_init.cc
@@ -69,7 +69,10 @@ std::unique_ptr<ash::mus::WindowManager> CreateMusShell() {
   std::unique_ptr<aura::WindowTreeClient> window_tree_client =
       base::MakeUnique<aura::WindowTreeClient>(connector, window_manager.get(),
                                                window_manager.get());
-  window_tree_client->ConnectAsWindowManager();
+  // In mus mode we want all events to dispatch from the Shell, so that pre
+  // target handlers and all that are correctly called.
+  const bool dispatch_from_host = true;
+  window_tree_client->ConnectAsWindowManager(dispatch_from_host);
   aura::Env::GetInstance()->SetWindowTreeClient(window_tree_client.get());
   window_manager->Init(std::move(window_tree_client),
                        content::BrowserThread::GetBlockingPool(),