Speculative workaround for a crash. Not sure how it could reach this state, b...

chrome/browser/net/passive_log_collector.cc

 // Copyright (c) 2010 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 "chrome/browser/net/passive_log_collector.h"
 
 #include <algorithm>
 
 #include "base/compiler_specific.h"
 #include "base/string_util.h"
@@ skipping 163 matching lines @@
           NOTREACHED();
           break;
       }
     }
   }
 }
 
 void PassiveLogCollector::SourceTracker::DeleteSourceInfo(
     uint32 source_id) {
   SourceIDToInfoMap::iterator it = sources_.find(source_id);
-  DCHECK(it != sources_.end());
+  if (it == sources_.end()) {
+    // TODO(eroman): Is this happening? And if so, why.
+    LOG(WARNING) << "Tried to delete info for nonexistent source";
+    return;
+  }
   // The source should not be in the deletion queue.
   DCHECK(std::find(deletion_queue_.begin(), deletion_queue_.end(),
                    source_id) == deletion_queue_.end());
   ReleaseAllReferencesToDependencies(&(it->second));
   sources_.erase(it);
 }
 
 void PassiveLogCollector::SourceTracker::Clear() {
   deletion_queue_.clear();
 
@@ skipping 252 matching lines @@
 PassiveLogCollector::SpdySessionTracker::DoAddEntry(const Entry& entry,
                                                     SourceInfo* out_info) {
   AddEntryToSourceInfo(entry, out_info);
   if (entry.type == net::NetLog::TYPE_SPDY_SESSION &&
       entry.phase == net::NetLog::PHASE_END) {
     return ACTION_MOVE_TO_GRAVEYARD;
   } else {
     return ACTION_NONE;
   }
 }