Don't clear the forward history when replacing entries.

content/browser/frame_host/navigation_controller_impl_browsertest.cc

 // Copyright 2014 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 "base/bind.h"
 #include "base/command_line.h"
 #include "base/strings/stringprintf.h"
 #include "content/browser/frame_host/frame_navigation_entry.h"
 #include "content/browser/frame_host/frame_tree.h"
 #include "content/browser/frame_host/navigation_controller_impl.h"
@@ skipping 168 matching lines @@
 // that the browser and renderer agree, and that both get it right.
 IN_PROC_BROWSER_TEST_F(NavigationControllerBrowserTest,
                        CorrectLengthWithCurrentItemReplacement) {
   NavigationController& controller =
       shell()->web_contents()->GetController();
 
   EXPECT_TRUE(NavigateToURL(shell(), GURL("data:text/html,page1")));
   EXPECT_EQ(1, controller.GetEntryCount());
   EXPECT_EQ(1, RendererHistoryLength(shell()));
 
-  EXPECT_TRUE(NavigateToURLAndReplace(shell(), GURL("data:text/html,page2")));
-  EXPECT_EQ(1, controller.GetEntryCount());
-  EXPECT_EQ(1, RendererHistoryLength(shell()));
+  EXPECT_TRUE(NavigateToURL(shell(), GURL("data:text/html,page2")));
+  EXPECT_EQ(2, controller.GetEntryCount());
+  EXPECT_EQ(2, RendererHistoryLength(shell()));
+
+  // Go back and then replace the first entry.
+  controller.GoBack();
+  EXPECT_TRUE(WaitForLoadStop(shell()->web_contents()));
+  EXPECT_TRUE(controller.CanGoForward());
+
+  EXPECT_TRUE(NavigateToURLAndReplace(shell(), GURL("data:text/html,page1b")));
+  EXPECT_EQ(2, controller.GetEntryCount());
+  EXPECT_EQ(2, RendererHistoryLength(shell()));
+  EXPECT_TRUE(controller.CanGoForward());

[Avi (use Gerrit), 2015/07/16 20:00:16]

Are you sure that this change keeps testing the same code in RenderView that the
old code did? More precisely, this is testing the "&&
!navigation_state->start_params().should_replace_current_entry" part of
RenderFrameImpl::didCommitProvisionalLoad. Can you delete that clause and make
sure that this test fails?

[Charlie Reis, 2015/07/16 20:17:43]

Good point.  The fact that I only had one additional entry made the expectation
(2) the same as the buggy answer from the renderer (2).  Sure enough, the test
passed when removing that clause.

I updated it in two ways: I preserved your original test (causing it to fail
without the RenderFrameImpl clause), and I changed my new case to have 3 entries
in history (which independently fails without the RenderFrameImpl clause).

 
   // Note that there's no way to access the renderer's notion of the history
   // offset via JavaScript. Checking just the history length, though, is enough;
   // if the replacement failed, there would be a new history entry and thus an
   // incorrect length.
 }
 
 // When spawning a new page from a WebUI page, make sure that the browser and
 // renderer agree about the length of the history list, and that both get it
 // right.
@@ skipping 1922 matching lines @@
     // tricky.
     EXPECT_EQ(nullptr, controller.GetPendingEntry());
     shell()->web_contents()->Stop();
     watcher.Wait();
   }
 
   ResourceDispatcherHost::Get()->SetDelegate(nullptr);
 }
 
 }  // namespace content