Fix tab drag and drop with hi-dpi.

chrome/browser/ui/views/tabs/tab_drag_controller.cc

Index: chrome/browser/ui/views/tabs/tab_drag_controller.cc
diff --git a/chrome/browser/ui/views/tabs/tab_drag_controller.cc b/chrome/browser/ui/views/tabs/tab_drag_controller.cc
index 644201dcab6a63db751e5924929a63e085d458a4..9349e51b078045f3066dd648ff77b12553963072 100644
--- a/chrome/browser/ui/views/tabs/tab_drag_controller.cc
+++ b/chrome/browser/ui/views/tabs/tab_drag_controller.cc
@@ -29,6 +29,7 @@
 #include "content/public/browser/user_metrics.h"
 #include "content/public/browser/web_contents.h"
 #include "extensions/browser/extension_function_dispatcher.h"
+#include "ui/compositor/dip_util.h"
 #include "ui/events/event_constants.h"
 #include "ui/events/gestures/gesture_recognizer.h"
 #include "ui/gfx/geometry/point_conversions.h"
@@ -1782,7 +1783,7 @@ gfx::Vector2d TabDragController::GetWindowOffset(
 }
 
 gfx::NativeWindow TabDragController::GetLocalProcessWindow(
-    const gfx::Point& screen_point,
+    gfx::Point screen_point,
     bool exclude_dragged_view) {
   std::set<gfx::NativeWindow> exclude;
   if (exclude_dragged_view) {
@@ -1805,8 +1806,14 @@ gfx::NativeWindow TabDragController::GetLocalProcessWindow(
       exclude.insert((*it)->window()->GetNativeWindow());
   }
 #endif
+
+#if defined(OS_LINUX) && defined(USE_AURA)
+  gfx::NativeWindow dragged_window =
+        attached_tabstrip_->GetWidget()->GetNativeWindow();
+  screen_point = ui::ConvertPointToPixel(dragged_window->layer(), screen_point);
+#endif

[sadrul, 2015/03/20 17:40:24]

This should actually happen in window_finder_x11.cc, right? That would make most
sense, since on Windows, we use DIP in the call to
GetLocalProcessWindowAtPoint(), and so we should also use DIP in the call to
GetLocalProcessWindowAtPoint() on Linux, but convert to pixels before calling
into X11TopmostWindowFinder.

[stapelberg, 2015/03/20 21:48:06]

Done. I really hope you won’t suggest _another_ location to try now :).

[sadrul, 2015/03/20 22:02:03]

Heh no. The new patchset looks good.

We need to make sure that the API we use is mostly consistent across platforms,
and so it's important to make sure we are using the same coordinate-space on
both Windows and Linux for GetLocalProcessWindowAtPoint() (which, in this case,
happens to be DIP).

+
   return GetLocalProcessWindowAtPoint(host_desktop_type_,
                                       screen_point,
                                       exclude);
-
 }