This patch improves the way that GuestViewManager tracks the destruction of GuestView embedders.

extensions/browser/guest_view/web_view/web_view_guest.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 "extensions/browser/guest_view/web_view/web_view_guest.h"
 
 #include "base/message_loop/message_loop.h"
 #include "base/strings/stringprintf.h"
 #include "base/strings/utf_string_conversions.h"
 #include "components/browsing_data/storage_partition_http_cache_data_remover.h"
@@ skipping 179 matching lines @@
 }
 
 using WebViewKey = std::pair<int, int>;
 using WebViewKeyToIDMap = std::map<WebViewKey, int>;
 static base::LazyInstance<WebViewKeyToIDMap> web_view_key_to_id_map =
     LAZY_INSTANCE_INITIALIZER;
 
 }  // namespace
 
 // static
-void WebViewGuest::CleanUp(int embedder_process_id, int view_instance_id) {
-  GuestViewBase::CleanUp(embedder_process_id, view_instance_id);
-
-  auto rph = content::RenderProcessHost::FromID(embedder_process_id);
-  // TODO(paulmeyer): It should be impossible for rph to be nullptr here, but
-  // this check is needed here for now as there seems to be occasional crashes
-  // because of this (http//crbug.com/499438). This should be removed once the
-  // cause is discovered and fixed.
-  DCHECK(rph != nullptr)
-      << "Cannot find RenderProcessHost for embedder process ID# "
-      << embedder_process_id;
-  if (rph == nullptr)
-    return;
-  auto browser_context = rph->GetBrowserContext();
+void WebViewGuest::CleanUp(content::BrowserContext* browser_context,
+                           int embedder_process_id,
+                           int view_instance_id) {
+  GuestViewBase::CleanUp(browser_context, embedder_process_id,
+                         view_instance_id);
 
   // Clean up rules registries for the WebView.
   WebViewKey key(embedder_process_id, view_instance_id);
   auto it = web_view_key_to_id_map.Get().find(key);
   if (it != web_view_key_to_id_map.Get().end()) {
     auto rules_registry_id = it->second;
     web_view_key_to_id_map.Get().erase(it);
-    RulesRegistryService::Get(browser_context)
-        ->RemoveRulesRegistriesByID(rules_registry_id);
+    RulesRegistryService* rrs =
+        RulesRegistryService::GetIfExists(browser_context);
+    if (rrs)
+      rrs->RemoveRulesRegistriesByID(rules_registry_id);
   }
 
   // Clean up web request event listeners for the WebView.
   content::BrowserThread::PostTask(
       content::BrowserThread::IO,
       FROM_HERE,
       base::Bind(
           &RemoveWebViewEventListenersOnIOThread,
           browser_context,
           embedder_process_id,
@@ skipping 1217 matching lines @@
     scoped_ptr<base::DictionaryValue> args(new base::DictionaryValue());
     DispatchEventToView(
         new GuestViewEvent(webview::kEventExitFullscreen, args.Pass()));
   }
   // Since we changed fullscreen state, sending a Resize message ensures that
   // renderer/ sees the change.
   web_contents()->GetRenderViewHost()->WasResized();
 }
 
 }  // namespace extensions