linux_aura: Improve window drag performance.

ui/views/widget/desktop_aura/x11_desktop_window_move_client.cc

Index: ui/views/widget/desktop_aura/x11_desktop_window_move_client.cc
diff --git a/ui/views/widget/desktop_aura/x11_desktop_window_move_client.cc b/ui/views/widget/desktop_aura/x11_desktop_window_move_client.cc
index 41573fece9a0b662decba46fc548292e769ddb34..651d6fa738e5c9b05536c8f3952c7578170a714f 100644
--- a/ui/views/widget/desktop_aura/x11_desktop_window_move_client.cc
+++ b/ui/views/widget/desktop_aura/x11_desktop_window_move_client.cc
@@ -18,6 +18,26 @@
 #include "ui/events/event.h"
 #include "ui/gfx/screen.h"
 
+namespace {
+
+// Delay moving the window.
+//
+// When we receive a mouse move event, we have to have it processed in a
+// different run through the message pump because moving the window will
+// otherwise prevent tasks from running.
+//
+// This constant was derived with playing with builds of chrome; it has no
+// theoretical justification.
+//
+// TODO(erg): This helps with the performance of dragging windows, but it
+// doesn't really solve the hard problems, which is that various calls to X11,
+// such as XQueryPointer, ui::IsWindowVisible() and ui::WindowContainsPoint()
+// take a while to get replies and block in the process. I've seen all of the
+// above take as long as 20ms to respond.
+const int kMoveDelay = 3;
+
+}  // namespace
+
 namespace views {
 
 X11DesktopWindowMoveClient::X11DesktopWindowMoveClient()
@@ -30,8 +50,15 @@ X11DesktopWindowMoveClient::~X11DesktopWindowMoveClient() {}
 void X11DesktopWindowMoveClient::OnMouseMovement(XMotionEvent* event) {
   gfx::Point cursor_point(event->x_root, event->y_root);
   gfx::Point system_loc = cursor_point - window_offset_;
-  root_window_->SetHostBounds(gfx::Rect(
-      system_loc, root_window_->GetHostSize()));
+
+  gfx::Rect target_rect(system_loc, root_window_->GetHostSize());
+
+  window_move_timer_.Start(
+      FROM_HERE,
+      base::TimeDelta::FromMilliseconds(kMoveDelay),
+      base::Bind(&X11DesktopWindowMoveClient::SetHostBounds,
+                 base::Unretained(this),
+                 target_rect));
 }
 
 void X11DesktopWindowMoveClient::OnMouseReleased() {
@@ -57,7 +84,15 @@ aura::client::WindowMoveResult X11DesktopWindowMoveClient::RunMoveLoop(
 }
 
 void X11DesktopWindowMoveClient::EndMoveLoop() {
+  window_move_timer_.Stop();
   move_loop_.EndMoveLoop();
 }
 
+////////////////////////////////////////////////////////////////////////////////
+// DesktopRootWindowHostLinux, private:
+
+void X11DesktopWindowMoveClient::SetHostBounds(const gfx::Rect& rect) {
+  root_window_->SetHostBounds(rect);
+}
+
 }  // namespace views