Additional fixes for prerender/instant + browsing history.

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 726 matching lines @@
   IPC_STRUCT_MEMBER(string16, frame_name)
 IPC_STRUCT_END()
 
 // Messages sent from the browser to the renderer.
 
 // Used typically when recovering from a crash.  The new rendering process
 // sets its global "next page id" counter to the given value.
 IPC_MESSAGE_CONTROL1(ViewMsg_SetNextPageID,
                      int32 /* next_page_id */)
 
-// Sets the history length of page_ids for a RenderView to
-// |length| entries, and moves the current page_id to the last
-// entry if it is valid.
-// The main use for this is prerendered pages, but Instant pages also use this.
-// For example, assume that there are 3 entries in the history when a
-// prerendered page is created. The new prerendered page will have a single
-// entry history like [7]. When it is swapped in, we need to extend the history
-// so it has a total length of 4 (3 for the previous history, 1 for the
-// prerendered page), so it looks like [-1 -1 -1 7].
-IPC_MESSAGE_ROUTED1(ViewMsg_SetHistoryLengthAndClear,
-                    int /* length */)
+// Sent to the RenderView when a prerendered or instant page is committed

[jam, 2011/08/15 15:59:10]

content layer doesn't know about prerendering/instant, so the comments shouldn't
mention them.

+// to an existing tab. The existing tab has a history of
+// |merged_history_length| which precedes the current history of pages
+// in the render view. All page_ids >= |minimum_page_id| are appended to
+// this new history in the same order.
+//
+// For example, suppose the history of page_ids in the instant RenderView
+// is [4 7 8]. This instant RenderView is committed, and merged into
+// an existing tab with 3 history items, with every page with page_id >= 7
+// is preserved. The resulting page history is [-1 -1 -1 7 8].
+IPC_MESSAGE_ROUTED2(ViewMsg_SetHistoryLengthAndPrune,
+                    int, /* merge_history_length */
+                    int32 /* minimum_page_id */)
 
 // Sends System Colors corresponding to a set of CSS color keywords
 // down the pipe.
 // This message must be sent to the renderer immediately on launch
 // before creating any new views.
 // The message can also be sent during a renderer's lifetime if system colors
 // are updated.
 // TODO(jeremy): Possibly change IPC format once we have this all hooked up.
 IPC_MESSAGE_ROUTED1(ViewMsg_SetCSSColors,
                     std::vector<CSSColors::CSSColorMapping>)
@@ skipping 1284 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 */)