Temporarily dump without crashing when setting an empty PageState.

content/browser/frame_host/navigation_entry_impl.cc

 // Copyright 2013 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/frame_host/navigation_entry_impl.h"
 
 #include <stddef.h>
 
 #include <queue>
 #include <utility>
 
+#include "base/debug/dump_without_crashing.h"
 #include "base/memory/ptr_util.h"
 #include "base/metrics/histogram.h"
 #include "base/strings/string_util.h"
 #include "base/strings/utf_string_conversions.h"
 #include "build/build_config.h"
 #include "components/url_formatter/url_formatter.h"
 #include "content/common/content_constants_internal.h"
 #include "content/common/navigation_params.h"
 #include "content/common/page_state_serialization.h"
 #include "content/common/resource_request_body_impl.h"
@@ skipping 23 matching lines @@
       state.document_sequence_number, nullptr, nullptr,
       GURL(state.url_string.string()),
       Referrer(GURL(state.referrer.string()), state.referrer_policy), "GET",
       -1);
 
   // Set a single-frame PageState on the entry.
   ExplodedPageState page_state;
   page_state.top = state;
   std::string data;
   EncodePageState(page_state, &data);
+  if (data.empty()) {
+    // Temporarily generate a minidump to diagnose https://crbug.com/568703.
+    base::debug::DumpWithoutCrashing();
+    NOTREACHED() << "Shouldn't generate an empty PageState.";
+  }
   node->frame_entry->set_page_state(PageState::CreateFromEncodedData(data));
 
   for (const ExplodedFrameState& child_state : state.children) {
     NavigationEntryImpl::TreeNode* child_node =
         new NavigationEntryImpl::TreeNode(nullptr);
     node->children.push_back(child_node);
     RecursivelyGenerateFrameEntries(child_state, child_node);
   }
 }
 
@@ skipping 257 matching lines @@
   // entries exist, but there's currently no way to check that.
   if (!frame_tree_->children.empty())
     frame_tree_->children.clear();
 
   // If the PageState can't be parsed or has no children, just store it on the
   // main frame's FrameNavigationEntry without recursively creating subframe
   // entries.
   ExplodedPageState exploded_state;
   if (!DecodePageState(state.ToEncodedData(), &exploded_state) ||
       exploded_state.top.children.size() == 0U) {
     frame_tree_->frame_entry->set_page_state(state);

[Charlie Reis, 2016/07/28 21:36:14]

I skipped this one because we temporarily set an empty PageState here on main
frames during tab sync restore.  I've verified that case doesn't lead to the
bug, and it's nontrivial to avoid setting the empty PageState (due to the way we
rewrite virtual URLs).

Given that most of the crashes we've seen have been subframes, I think this spot
is unlikely to be the cause.

[nasko, 2016/07/28 21:42:58]

Acknowledged.

     return;
   }
 
   RecursivelyGenerateFrameEntries(exploded_state.top, frame_tree_.get());
 }
 
 PageState NavigationEntryImpl::GetPageState() const {
   // Just return the main frame's PageState in default Chrome, or if there are
   // no subframe FrameNavigationEntries.
   if (!SiteIsolationPolicy::UseSubframeNavigationEntries() ||
@@ skipping 421 matching lines @@
     }
   }
 
   // No entry exists yet, so create a new one.
   // Unordered list, since we expect to look up entries by frame sequence number
   // or unique name.
   FrameNavigationEntry* frame_entry = new FrameNavigationEntry(
       unique_name, item_sequence_number, document_sequence_number,
       site_instance, std::move(source_site_instance), url, referrer, method,
       post_id);
+  if (!page_state.IsValid()) {
+    // Temporarily generate a minidump to diagnose https://crbug.com/568703.
+    base::debug::DumpWithoutCrashing();
+    NOTREACHED() << "Shouldn't set an empty PageState.";
+  }
   frame_entry->set_page_state(page_state);
   parent_node->children.push_back(
       new NavigationEntryImpl::TreeNode(frame_entry));
 }
 
 FrameNavigationEntry* NavigationEntryImpl::GetFrameEntry(
     FrameTreeNode* frame_tree_node) const {
   NavigationEntryImpl::TreeNode* tree_node = FindFrameEntry(frame_tree_node);
   return tree_node ? tree_node->frame_entry.get() : nullptr;
 }
@@ skipping 27 matching lines @@
       return node;
 
     // Enqueue any children and keep looking.
     for (auto* child : node->children)
       work_queue.push(child);
   }
   return nullptr;
 }
 
 }  // namespace content