Fix tab drag and drop with hi-dpi.

ui/views/widget/desktop_aura/desktop_screen_x11.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ui/views/widget/desktop_aura/desktop_screen_x11.h"
 
 #include <X11/extensions/Xrandr.h>
 #include <X11/Xlib.h>
 
 // It clashes with out RootWindow.
@@ skipping 27 matching lines @@
   const int kCSSDefaultDPI = 96;
   const float kInchInMm = 25.4f;
 
   float screen_inches = screen_mm / kInchInMm;
   float screen_dpi = screen_pixels / screen_inches;
   float scale = screen_dpi / kCSSDefaultDPI;
 
   return ui::GetScaleForScaleFactor(ui::GetSupportedScaleFactor(scale));
 }
 
+float GetDeviceScaleFactor() {
+  gfx::Display display = gfx::Screen::GetNativeScreen()->GetPrimaryDisplay();
+  return display.device_scale_factor();
+}
+
+gfx::Point PixelToDIPPoint(const gfx::Point& pixel_point) {
+  return ToFlooredPoint(ScalePoint(pixel_point, 1.0f / GetDeviceScaleFactor()));
+}
+
+gfx::Point DIPToPixelPoint(const gfx::Point& dip_point) {
+  return ToFlooredPoint(gfx::ScalePoint(dip_point, GetDeviceScaleFactor()));
+}
+
 std::vector<gfx::Display> GetFallbackDisplayList() {
   ::XDisplay* display = gfx::GetXDisplay();
   ::Screen* screen = DefaultScreenOfDisplay(display);
   int width = WidthOfScreen(screen);
   int height = HeightOfScreen(screen);
   gfx::Size physical_size(WidthMMOfScreen(screen), HeightMMOfScreen(screen));
 
   gfx::Rect bounds_in_pixels(0, 0, width, height);
   gfx::Display gfx_display(0, bounds_in_pixels);
   if (!gfx::Display::HasForceDeviceScaleFactor() &&
@@ skipping 65 matching lines @@
   XQueryPointer(display,
                 DefaultRootWindow(display),
                 &root,
                 &child,
                 &root_x,
                 &root_y,
                 &win_x,
                 &win_y,
                 &mask);
 
-  return gfx::Point(root_x, root_y);
+  return PixelToDIPPoint(gfx::Point(root_x, root_y));
 }
 
 gfx::NativeWindow DesktopScreenX11::GetWindowUnderCursor() {
   return GetWindowAtScreenPoint(GetCursorScreenPoint());
 }
 
 gfx::NativeWindow DesktopScreenX11::GetWindowAtScreenPoint(
     const gfx::Point& point) {
   X11TopmostWindowFinder finder;
-  return finder.FindLocalProcessWindowAt(point, std::set<aura::Window*>());
+  return finder.FindLocalProcessWindowAt(
+      DIPToPixelPoint(point), std::set<aura::Window*>());
 }
 
 int DesktopScreenX11::GetNumDisplays() const {
   return displays_.size();
 }
 
 std::vector<gfx::Display> DesktopScreenX11::GetAllDisplays() const {
   return displays_;
 }
 
@@ skipping 16 matching lines @@
     DesktopWindowTreeHostX11* rwh = DesktopWindowTreeHostX11::GetHostForXID(
         host->GetAcceleratedWidget());
     if (rwh)
       return GetDisplayMatching(rwh->GetX11RootWindowBounds());
   }
 
   return GetPrimaryDisplay();
 }
 
 gfx::Display DesktopScreenX11::GetDisplayNearestPoint(
-    const gfx::Point& point) const {
+    const gfx::Point& requested_point) const {
+  const gfx::Point point_in_pixel = DIPToPixelPoint(requested_point);
   for (std::vector<gfx::Display>::const_iterator it = displays_.begin();
        it != displays_.end(); ++it) {
-    if (it->bounds().Contains(point))
+    if (it->bounds().Contains(point_in_pixel))
       return *it;
   }
 
   return GetPrimaryDisplay();
 }
 
 gfx::Display DesktopScreenX11::GetDisplayMatching(
     const gfx::Rect& match_rect) const {
   int max_area = 0;
   const gfx::Display* matching = NULL;
@@ skipping 164 matching lines @@
   change_notifier_.NotifyDisplaysChanged(old_displays, displays_);
 }
 
 ////////////////////////////////////////////////////////////////////////////////
 
 gfx::Screen* CreateDesktopScreen() {
   return new DesktopScreenX11;
 }
 
 }  // namespace views