Fix nullptr dereference of a RenderProcessHost

content/browser/renderer_host/render_process_host_impl.cc

 // Copyright 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.
 
 // Represents the browser side of the browser <--> renderer communication
 // channel. There will be one RenderProcessHost per renderer process.
 
 #include "content/browser/renderer_host/render_process_host_impl.h"
 
 #include <algorithm>
@@ skipping 677 matching lines @@
       const GURL& site_url,
       std::set<RenderProcessHost*>* foreground_processes,
       std::set<RenderProcessHost*>* background_processes) {
     auto result = map_.find(site_url);
     if (result == map_.end())
       return;
 
     std::map<ProcessID, Count>& counts_per_process = result->second;
     for (auto iter : counts_per_process) {
       RenderProcessHost* host = RenderProcessHost::FromID(iter.first);
-      DCHECK(host);
+      if (!host) {
+        // TODO(clamy): This shouldn't happen but we are getting reports from
+        // the field that this is happening. We need to figure out why some
+        // RenderProcessHosts are not taken out of the map when they're
+        // destroyed.
+        NOTREACHED();
+        continue;
+      }
       if (host->VisibleWidgetCount())
         foreground_processes->insert(host);
       else
         background_processes->insert(host);
     }
   }
 
  private:
   void RenderProcessHostDestroyed(RenderProcessHost* host) override {
 #ifndef NDEBUG
@@ skipping 2920 matching lines @@
   LOG(ERROR) << "Terminating render process for bad Mojo message: " << error;
 
   // The ReceivedBadMessage call below will trigger a DumpWithoutCrashing.
   // Capture the error message in a crash key value.
   base::debug::ScopedCrashKey error_key_value("mojo-message-error", error);
   bad_message::ReceivedBadMessage(render_process_id,
                                   bad_message::RPH_MOJO_PROCESS_ERROR);
 }
 
 }  // namespace content