Differentiate invisible cursor mode and disabled mouse events mode.

content/common/view_messages.h

Index: content/common/view_messages.h
diff --git a/content/common/view_messages.h b/content/common/view_messages.h
index 089f9e51c8ef03a03dc4a08113d3a40484d60c12..bf5e42503b9d9d2e9492734f98269ee3364b5399 100644
--- a/content/common/view_messages.h
+++ b/content/common/view_messages.h
@@ -1826,6 +1826,13 @@ IPC_MESSAGE_ROUTED1(ViewHostMsg_OpenURL, ViewHostMsg_OpenURL_Params)
 IPC_MESSAGE_ROUTED1(ViewHostMsg_DidContentsPreferredSizeChange,
                     gfx::Size /* pref_size */)
 
+// Notifies that the scroll offset changed.
+// This is different from ViewHostMsg_UpdateRect_Params's scroll_offset in
+// that ViewHostMsg_UpdateRect is not sent at all when threaded compositing is
+// enabled while ViewHostMsg_DidChangeScrollOffset works properly in this case.
+IPC_MESSAGE_ROUTED1(ViewHostMsg_DidChangeScrollOffset,
+                    gfx::Vector2d /* offset */)
+
 // Notifies that the scrollbars-visible state of the content changed.
 IPC_MESSAGE_ROUTED2(ViewHostMsg_DidChangeScrollOffsetPinningForMainFrame,
                     bool /* has_horizontal_scrollbar */,