Pipe "is pinned to left/right", "has horizontal/vertical scrollbar",

content/common/view_messages.h

 // Copyright (c) 2011 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.
 
 // IPC messages for page rendering.
 // Multiply-included message file, hence no include guard.
 
 #include "base/process.h"
 #include "base/shared_memory.h"
 #include "content/common/common_param_traits.h"
@@ skipping 1644 matching lines @@
 // Requests that the given URL be opened in the specified manner.
 IPC_MESSAGE_ROUTED3(ViewHostMsg_OpenURL,
                     GURL /* url */,
                     GURL /* referrer */,
                     WindowOpenDisposition /* disposition */)
 
 // Notifies that the preferred size of the content changed.
 IPC_MESSAGE_ROUTED1(ViewHostMsg_DidContentsPreferredSizeChange,
                     gfx::Size /* pref_size */)
 
+// Notifies that the scrollbars-visible state of the content changed.
+IPC_MESSAGE_ROUTED2(ViewHostMsg_DidChangeScrollOffsetPinningForMainFrame,
+                    bool /* has_horizontal_scrollbar */,
+                    bool /* has_vertical_scrollbar */)
+
+// Notifies that the pinned-to-side state of the content changed.
+IPC_MESSAGE_ROUTED2(ViewHostMsg_DidChangeScrollbarsForMainFrame,
+                    bool /* pinned_to_left */,
+                    bool /* pinned_to_right */)
+
+// Notifies that the number of JavaScript scroll handlers changed.
+IPC_MESSAGE_ROUTED1(ViewHostMsg_DidChangeNumWheelEvents,
+                    int /* count */)
+
 // A message from HTML-based UI.  When (trusted) Javascript calls
 // send(message, args), this message is sent to the browser.
 IPC_MESSAGE_ROUTED3(ViewHostMsg_WebUISend,
                     GURL /* source_url */,
                     std::string  /* message */,
                     base::ListValue /* args */)
 
 // A renderer sends this to the browser process when it wants to
 // create a ppapi plugin.  The browser will create the plugin process if
 // necessary, and will return a handle to the channel on success.
@@ skipping 380 matching lines @@
                     int32 /* complete status */)
 
 // Request updated information about the client firewall traversal policy.
 // Will result in a ViewMsg_UpdateRemoteAccessClientFirewallTraversal message
 // being sent back.
 IPC_MESSAGE_ROUTED0(ViewHostMsg_RequestRemoteAccessClientFirewallTraversal)
 
 // Notifies the browser of an event occurring in the media pipeline.
 IPC_MESSAGE_CONTROL1(ViewHostMsg_MediaLogEvent,
                      media::MediaLogEvent /* event */)