Remove DumpWithoutCrashing calls for empty PageState.

content/browser/web_contents/web_contents_impl.cc

 // Copyright (c) 2012 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 "content/browser/web_contents/web_contents_impl.h"
 
 #include <stddef.h>
 
 #include <cmath>
 #include <utility>
 #include <vector>
 
 #include "base/command_line.h"
-#include "base/debug/dump_without_crashing.h"
 #include "base/feature_list.h"
 #include "base/i18n/character_encoding.h"
 #include "base/lazy_instance.h"
 #include "base/location.h"
 #include "base/logging.h"
 #include "base/macros.h"
 #include "base/memory/ptr_util.h"
 #include "base/memory/ref_counted.h"
 #include "base/metrics/histogram_macros.h"
 #include "base/process/process.h"
@@ skipping 4577 matching lines @@
   // The SiteInstance might not match if we do a cross-process navigation with
   // replacement (e.g., auto-subframe), in which case the swap out of the old
   // RenderFrameHost runs in the background after the old FrameNavigationEntry
   // has already been replaced and destroyed.
   if (frame_entry->site_instance() != rfhi->GetSiteInstance())
     return;
 
   if (page_state == frame_entry->page_state())
     return;  // Nothing to update.
 
-  if (!page_state.IsValid()) {
-    // Temporarily generate a minidump to diagnose https://crbug.com/568703.
-    base::debug::DumpWithoutCrashing();

[alexmos, 2017/02/23 18:05:12]

Ha, I actually found one of these!  See b310b2c700000000.  That's the only one I
could find though.

(The way I checked was to look up all the crashes that include
WCI::UpdateStateForFrame on the stack.  Then in the signatures, find the one for
dump without crashing.  Then look at the authors -- most of them were from Nasko
diagnosing another bug, and one was here.)

[Charlie Reis, 2017/02/28 05:30:57]

Wow, interesting.  And another one just came in: 0a83443300000000.

That's pretty low volume, though, so I'll just look into the report to see what
I can learn and still remove the DumpWithoutCrashing.  As before, I'll leave a
DCHECK in its place.

-    NOTREACHED() << "Shouldn't set an empty PageState.";
-  }
-
   // The document_sequence_number and item_sequence_number recorded in the
   // FrameNavigationEntry should not differ from the one coming with the update,
   // since it must come from the same document. Do not update it if a difference
   // is detected, as this indicates that |frame_entry| is not the correct one.
   ExplodedPageState exploded_state;
   if (!DecodePageState(page_state.ToEncodedData(), &exploded_state))
     return;
 
   if (exploded_state.top.document_sequence_number !=
           frame_entry->document_sequence_number() ||
@@ skipping 800 matching lines @@
     RenderViewHost* render_view_host = RenderViewHost::From(render_widget_host);
     if (!render_view_host)
       continue;
     render_view_host_set.insert(render_view_host);
   }
   for (RenderViewHost* render_view_host : render_view_host_set)
     render_view_host->OnWebkitPreferencesChanged();
 }
 
 }  // namespace content