Do not release capture when transferring capture between Chrome windows on Linux

ui/views/widget/desktop_aura/desktop_window_tree_host_x11.cc

Index: ui/views/widget/desktop_aura/desktop_window_tree_host_x11.cc
diff --git a/ui/views/widget/desktop_aura/desktop_window_tree_host_x11.cc b/ui/views/widget/desktop_aura/desktop_window_tree_host_x11.cc
index d428447e84aefcfdd8417359069c6921002b94ac..77c5966f8e4bc873bf5a71e3f306981b1201ecbe 100644
--- a/ui/views/widget/desktop_aura/desktop_window_tree_host_x11.cc
+++ b/ui/views/widget/desktop_aura/desktop_window_tree_host_x11.cc
@@ -18,6 +18,7 @@
 #include "third_party/skia/include/core/SkPath.h"
 #include "ui/aura/client/cursor_client.h"
 #include "ui/aura/client/focus_client.h"
+#include "ui/aura/client/screen_position_client.h"
 #include "ui/aura/window.h"
 #include "ui/aura/window_event_dispatcher.h"
 #include "ui/aura/window_property.h"
@@ -46,9 +47,9 @@
 #include "ui/views/widget/desktop_aura/desktop_native_cursor_manager.h"
 #include "ui/views/widget/desktop_aura/desktop_native_widget_aura.h"
 #include "ui/views/widget/desktop_aura/desktop_window_tree_host_observer_x11.h"
+#include "ui/views/widget/desktop_aura/x11_capture_window.h"
 #include "ui/views/widget/desktop_aura/x11_desktop_handler.h"
 #include "ui/views/widget/desktop_aura/x11_desktop_window_move_client.h"
-#include "ui/views/widget/desktop_aura/x11_scoped_capture.h"
 #include "ui/views/widget/desktop_aura/x11_window_event_filter.h"
 #include "ui/wm/core/compound_event_filter.h"
 #include "ui/wm/core/window_util.h"
@@ -901,24 +902,35 @@ gfx::Point DesktopWindowTreeHostX11::GetLocationOnNativeScreen() const {
 }
 
 void DesktopWindowTreeHostX11::SetCapture() {
-  // This is vaguely based on the old NativeWidgetGtk implementation.
-  //
-  // X11's XPointerGrab() shouldn't be used for everything; it doesn't map
-  // cleanly to Windows' SetCapture(). GTK only provides a separate concept of
-  // a grab that wasn't the X11 pointer grab, but was instead a manual
-  // redirection of the event. (You need to drop into GDK if you want to
-  // perform a raw X11 grab).
+  DesktopWindowTreeHostX11* old_capture = g_current_capture;
+  g_current_capture = this;
+  if (old_capture) {
+    // Take ownership of |old_capture|'s capture window which already has a
+    // mouse grab. Because there is no X11 mouse grab or mouse ungrab, the
+    // capture change is sychronous.
+    capture_window_ = old_capture->ReleaseCaptureWindow().Pass();
 
-  if (g_current_capture)
-    g_current_capture->OnCaptureReleased();
+    old_capture->OnHostLostWindowCapture();
+  }
 
-  g_current_capture = this;
-  x11_capture_.reset(new X11ScopedCapture(xwindow_));
+  if (!capture_window_) {
+    // Create an X11CaptureWindow to asynchronously grab the mouse. As
+    // |xwindow_| is likely the topmost window underneath the mouse, we will
+    // likely not miss any mouse events.
+    capture_window_.reset(new X11CaptureWindow);
+  }
 }
 
 void DesktopWindowTreeHostX11::ReleaseCapture() {
-  if (g_current_capture == this)
-    g_current_capture->OnCaptureReleased();
+  if (g_current_capture == this) {
+    // Release mouse grab asynchronously. |xwindow_| is likely the topmost
+    // window underneath the mouse so the capture release being asynchronous is
+    // likely inconsequential.
+    g_current_capture = NULL;
+    capture_window_.reset();
+
+    OnHostLostWindowCapture();
+  }
 }
 
 void DesktopWindowTreeHostX11::SetCursorNative(gfx::NativeCursor cursor) {
@@ -1300,10 +1312,8 @@ void DesktopWindowTreeHostX11::SetUseNativeFrame(bool use_native_frame) {
   ResetWindowRegion();
 }
 
-void DesktopWindowTreeHostX11::OnCaptureReleased() {
-  x11_capture_.reset();
-  g_current_capture = NULL;
-  OnHostLostWindowCapture();
+scoped_ptr<X11CaptureWindow> DesktopWindowTreeHostX11::ReleaseCaptureWindow() {
+  return capture_window_.Pass();
 }
 
 void DesktopWindowTreeHostX11::DispatchMouseEvent(ui::MouseEvent* event) {
@@ -1337,17 +1347,27 @@ void DesktopWindowTreeHostX11::DispatchMouseEvent(ui::MouseEvent* event) {
   if (event->IsAnyButton() || event->IsMouseWheelEvent())
     FlashFrame(false);
 
+  if (ui::EventTargetFromNative(event->native_event()) != xwindow_) {
+    // The event was targeted at |capture_window_|'s X window.
+    gfx::Point location =
+        ui::EventSystemLocationFromNative(event->native_event());
+    aura::client::GetScreenPositionClient(window())->ConvertPointFromScreen(
+        window(), &location);
+    event->set_location(location);
+  }
+
   if (!g_current_capture || g_current_capture == this) {
     SendEventToProcessor(event);
   } else {
-    // Another DesktopWindowTreeHostX11 has installed itself as
-    // capture. Translate the event's location and dispatch to the other.
+    // Another DesktopWindowTreeHostX11 has capture. Translate the event's
+    // location and dispatch to the other DesktopWindowTreeHostX11.
     event->ConvertLocationToTarget(window(), g_current_capture->window());
     g_current_capture->SendEventToProcessor(event);
   }
 }
 
 void DesktopWindowTreeHostX11::DispatchTouchEvent(ui::TouchEvent* event) {
+  DCHECK_EQ(ui::EventTargetFromNative(event->native_event()), xwindow_);
   if (g_current_capture && g_current_capture != this &&
       event->type() == ui::ET_TOUCH_PRESSED) {
     event->ConvertLocationToTarget(window(), g_current_capture->window());
@@ -1526,9 +1546,9 @@ void DesktopWindowTreeHostX11::Relayout() {
 
 bool DesktopWindowTreeHostX11::CanDispatchEvent(
     const ui::PlatformEvent& event) {
-  return event->xany.window == xwindow_ ||
-         (event->type == GenericEvent &&
-          static_cast<XIDeviceEvent*>(event->xcookie.data)->event == xwindow_);
+  XID target = ui::EventTargetFromNative(event);
+  return target == xwindow_ ||
+      (capture_window_ && target == capture_window_->xwindow());
 }
 
 uint32_t DesktopWindowTreeHostX11::DispatchEvent(
@@ -1554,6 +1574,11 @@ uint32_t DesktopWindowTreeHostX11::DispatchEvent(
 
       ui::MouseEvent mouse_event(xev);
       DispatchMouseEvent(&mouse_event);
+
+      if (xev->xcrossing.mode == NotifyGrab ||
+          xev->xcrossing.mode == NotifyUngrab) {
+        ReleaseCapture();
+      }
       break;
     }
     case Expose: {