Support multi-button press for synthetic mouse events

content/common/input/synthetic_web_input_event_builders.cc

Index: content/common/input/synthetic_web_input_event_builders.cc
diff --git a/content/common/input/synthetic_web_input_event_builders.cc b/content/common/input/synthetic_web_input_event_builders.cc
index c278f8f2608032b1e6d8bc217d0427786ef9d02a..e7c5f6da90adde6b5751b78181bea1a49e857603 100644
--- a/content/common/input/synthetic_web_input_event_builders.cc
+++ b/content/common/input/synthetic_web_input_event_builders.cc
@@ -37,12 +37,8 @@ WebMouseEvent SyntheticWebMouseEventBuilder::Build(
   result.y = window_y;
   result.windowX = window_x;
   result.windowY = window_y;
-
-  if (type == WebInputEvent::MouseDown || type == WebInputEvent::MouseUp)
-    result.button = WebMouseEvent::Button::Left;
-  else
-    result.button = WebMouseEvent::Button::NoButton;
-
+  result.setModifiers(modifiers);
+  result.pointerType = blink::WebPointerProperties::PointerType::Mouse;
   return result;
 }