Add Vector2d classes that represent offsets, instead of using Point.

ui/views/controls/table/table_view_win.cc

Index: ui/views/controls/table/table_view_win.cc
diff --git a/ui/views/controls/table/table_view_win.cc b/ui/views/controls/table/table_view_win.cc
index 1538dd858402934b0c0389869c25a02097104eb2..e8becd281452bc8e68eb7aae27b84924dd73e741 100644
--- a/ui/views/controls/table/table_view_win.cc
+++ b/ui/views/controls/table/table_view_win.cc
@@ -709,9 +709,9 @@ LRESULT CALLBACK TableView::TableWndProc(HWND window,
 
     case WM_MOUSEMOVE: {
       if (in_mouse_down) {
-        int x = GET_X_LPARAM(l_param);
-        int y = GET_Y_LPARAM(l_param);
-        if (View::ExceededDragThreshold(x - mouse_down_x, y - mouse_down_y)) {
+        gfx::Point mouse_pos(GET_X_LPARAM(l_param), GET_Y_LPARAM(l_param));
+        gfx::Point mouse_down_pos(mouse_down_x, mouse_down_y);
+        if (View::ExceededDragThreshold(mouse_pos - mouse_down_pos)) {
           // We're about to start drag and drop, which results in no mouse up.
           // Release capture and reset state.
           ReleaseCapture();