linux-aura: Fix some dragging behaviour.

ui/views/widget/desktop_aura/x11_whole_screen_move_loop.cc

Index: ui/views/widget/desktop_aura/x11_whole_screen_move_loop.cc
diff --git a/ui/views/widget/desktop_aura/x11_whole_screen_move_loop.cc b/ui/views/widget/desktop_aura/x11_whole_screen_move_loop.cc
index 20c061bd670c2914ab5836afc15edd6c790f8aa2..fd4b214e106f338a987c4ce486368dd5002b50c3 100644
--- a/ui/views/widget/desktop_aura/x11_whole_screen_move_loop.cc
+++ b/ui/views/widget/desktop_aura/x11_whole_screen_move_loop.cc
@@ -50,6 +50,7 @@ X11WholeScreenMoveLoop::X11WholeScreenMoveLoop(
     X11WholeScreenMoveLoopDelegate* delegate)
     : delegate_(delegate),
       in_move_loop_(false),
+      should_reset_mouse_flags_(false),
       grab_input_window_(None) {
 }
 
@@ -113,7 +114,11 @@ bool X11WholeScreenMoveLoop::RunMoveLoop(aura::Window* source,
   // We are handling a mouse drag outside of the aura::RootWindow system. We
   // must manually make aura think that the mouse button is pressed so that we
   // don't draw extraneous tooltips.
-  aura::Env::GetInstance()->set_mouse_button_flags(ui::EF_LEFT_MOUSE_BUTTON);
+  aura::Env* env = aura::Env::GetInstance();
+  if (!env->IsMouseButtonDown()) {
+    env->set_mouse_button_flags(ui::EF_LEFT_MOUSE_BUTTON);
+    should_reset_mouse_flags_ = true;
+  }
 
   base::MessageLoopForUI* loop = base::MessageLoopForUI::current();
   base::MessageLoop::ScopedNestableTaskAllower allow_nested(loop);
@@ -133,7 +138,10 @@ void X11WholeScreenMoveLoop::EndMoveLoop() {
     return;
 
   // We undo our emulated mouse click from RunMoveLoop();
-  aura::Env::GetInstance()->set_mouse_button_flags(0);
+  if (should_reset_mouse_flags_) {
+    aura::Env::GetInstance()->set_mouse_button_flags(0);
+    should_reset_mouse_flags_ = false;
+  }
 
   // TODO(erg): Is this ungrab the cause of having to click to give input focus
   // on drawn out windows? Not ungrabbing here screws the X server until I kill