Use changed_button_flags() when converting MouseEvent to blink::WebMouseEvent.

content/browser/renderer_host/web_input_event_aura.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 "content/browser/renderer_host/web_input_event_aura.h"
 
 #include "content/browser/renderer_host/ui_events_helper.h"
 #include "ui/aura/window.h"
 #include "ui/events/event.h"
 #include "ui/events/event_utils.h"
@@ skipping 295 matching lines @@
   return gesture_event;
 }
 
 blink::WebMouseEvent MakeWebMouseEventFromAuraEvent(ui::MouseEvent* event) {
   blink::WebMouseEvent webkit_event;
 
   webkit_event.modifiers = EventFlagsToWebEventModifiers(event->flags());
   webkit_event.timeStampSeconds = event->time_stamp().InSecondsF();
 
   webkit_event.button = blink::WebMouseEvent::ButtonNone;
-  if (event->flags() & ui::EF_LEFT_MOUSE_BUTTON)
+  int button_flags = event->flags();
+  if (event->type() == ui::ET_MOUSE_PRESSED ||
+      event->type() == ui::ET_MOUSE_RELEASED) {
+    // We want to use changed_button_flags() for mouse pressed & released.
+    // These flags can be used only if they are set which is not always the case
+    // (see e.g. GetChangedMouseButtonFlagsFromNative() in events_win.cc).
+    if (event->changed_button_flags())
+      button_flags = event->changed_button_flags();
+  }
+  if (button_flags & ui::EF_LEFT_MOUSE_BUTTON)
     webkit_event.button = blink::WebMouseEvent::ButtonLeft;
-  if (event->flags() & ui::EF_MIDDLE_MOUSE_BUTTON)
+  if (button_flags & ui::EF_MIDDLE_MOUSE_BUTTON)
     webkit_event.button = blink::WebMouseEvent::ButtonMiddle;
-  if (event->flags() & ui::EF_RIGHT_MOUSE_BUTTON)
+  if (button_flags & ui::EF_RIGHT_MOUSE_BUTTON)
     webkit_event.button = blink::WebMouseEvent::ButtonRight;
 
   switch (event->type()) {
     case ui::ET_MOUSE_PRESSED:
       webkit_event.type = blink::WebInputEvent::MouseDown;
       webkit_event.clickCount = event->GetClickCount();
       break;
     case ui::ET_MOUSE_RELEASED:
       webkit_event.type = blink::WebInputEvent::MouseUp;
       webkit_event.clickCount = event->GetClickCount();
@@ skipping 29 matching lines @@
     webkit_event.deltaY = event->y_offset();
   }
 
   webkit_event.wheelTicksX = webkit_event.deltaX / kPixelsPerTick;
   webkit_event.wheelTicksY = webkit_event.deltaY / kPixelsPerTick;
 
   return webkit_event;
 }
 
 }  // namespace content