cros: Fix potential null-deref when sleeping system on views-lock.

chrome/browser/chromeos/power/renderer_freezer.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 "chrome/browser/chromeos/power/renderer_freezer.h"
 
 #include <string>
 #include <utility>
 
 #include "base/bind.h"
@@ skipping 130 matching lines @@
 
 void RendererFreezer::OnScreenLockStateChanged(chromeos::ScreenLocker* locker,
                                                bool is_locked) {
   // The ScreenLocker class sends NOTIFICATION_SCREEN_LOCK_STATE_CHANGED when
   // the lock screen becomes ready, resulting in this code running synchronously
   // to mark the screen locker renderer to remain unfrozen during a suspend
   // request.  Since this happens before the PowerManagerClient calls
   // RendererFreezer::SuspendImminent(), it is guaranteed that the screen locker
   // renderer will not be frozen at any point.
   if (is_locked) {
-    delegate_->SetShouldFreezeRenderer(locker->delegate()
-                                           ->GetWebContents()
-                                           ->GetRenderProcessHost()
-                                           ->GetHandle(),
-                                       false);
+    content::WebContents* web_contents = locker->delegate()->GetWebContents();
+    if (web_contents) {

[Daniel Erat, 2017/05/26 22:10:06]

nit: mind adding a comment here mentioning why this is null? (or TODO pointing
at a bug, if the plan is to switch to the views-based lock screen and this can
be removed later)

[jdufault, 2017/05/26 23:15:20]

Done.

+      delegate_->SetShouldFreezeRenderer(
+          web_contents->GetRenderProcessHost()->GetHandle(), false);
+    }
   }
 }
 
 void RendererFreezer::OnRenderProcessCreated(content::RenderProcessHost* rph) {
   const int rph_id = rph->GetID();
 
   if (gcm_extension_processes_.find(rph_id) != gcm_extension_processes_.end()) {
     LOG(ERROR) << "Received duplicate notifications about the creation of a "
                << "RenderProcessHost with id " << rph_id;
     return;
@@ skipping 33 matching lines @@
     rph->AddObserver(this);
     return;
   }
 
   // We didn't find an extension in this RenderProcessHost that is using GCM so
   // we can go ahead and freeze it on suspend.
   delegate_->SetShouldFreezeRenderer(rph->GetHandle(), true);
 }
 
 }  // namespace chromeos