Support buttons attribute for drag event (chromium side).

ui/views/widget/desktop_aura/desktop_drag_drop_client_aurax11.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_drag_drop_client_aurax11.h"
 
 #include <X11/Xatom.h>
 
 #include "base/event_types.h"
 #include "base/lazy_instance.h"
@@ skipping 83 matching lines @@
                 &mask);
   int modifiers = ui::EF_NONE;
   if (mask & ShiftMask)
     modifiers |= ui::EF_SHIFT_DOWN;
   if (mask & ControlMask)
     modifiers |= ui::EF_CONTROL_DOWN;
   if (mask & Mod1Mask)
     modifiers |= ui::EF_ALT_DOWN;
   if (mask & Mod4Mask)
     modifiers |= ui::EF_COMMAND_DOWN;
+  if (mask & Button1Mask)
+    modifiers |= ui::EF_LEFT_MOUSE_BUTTON;
+  if (mask & Button2Mask)
+    modifiers |= ui::EF_MIDDLE_MOUSE_BUTTON;
+  if (mask & Button3Mask)
+    modifiers |= ui::EF_RIGHT_MOUSE_BUTTON;
   return modifiers;
 }
 
 // The time to wait for the target to respond after the user has released the
 // mouse button before ending the move loop.
 const int kEndMoveLoopTimeoutMs = 1000;
 
 // The time to wait since sending the last XdndPosition message before
 // reprocessing the most recent mouse move event in case that the window
 // stacking order has changed and |source_current_window_| needs to be updated.
@@ skipping 643 matching lines @@
     int flags,
     base::TimeDelta event_time) {
   if (drag_widget_.get()) {
     drag_widget_->SetBounds(
         gfx::Rect(screen_point - drag_widget_offset_,
                   drag_widget_->GetWindowBoundsInScreen().size()));
     drag_widget_->StackAtTop();
   }
 
   const int kModifiers = ui::EF_SHIFT_DOWN | ui::EF_CONTROL_DOWN |
-                         ui::EF_ALT_DOWN | ui::EF_COMMAND_DOWN;
+                         ui::EF_ALT_DOWN | ui::EF_COMMAND_DOWN |
+                         ui::EF_LEFT_MOUSE_BUTTON |
+                         ui::EF_MIDDLE_MOUSE_BUTTON |
+                         ui::EF_RIGHT_MOUSE_BUTTON;
   current_modifier_state_ = flags & kModifiers;
 
   repeat_mouse_move_timer_.Stop();
   ProcessMouseMove(screen_point, event_time.InMilliseconds());
 }
 
 void DesktopDragDropClientAuraX11::OnMouseReleased() {
   repeat_mouse_move_timer_.Stop();
 
   if (source_state_ != SOURCE_STATE_OTHER) {
@@ skipping 431 matching lines @@
     for (int x = 0; x < in_bitmap->width(); ++x) {
       if (SkColorGetA(in_row[x]) > kMinAlpha)
         return true;
     }
   }
 
   return false;
 }
 
 }  // namespace views