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

chrome/browser/chromeos/power/renderer_freezer.cc

Index: chrome/browser/chromeos/power/renderer_freezer.cc
diff --git a/chrome/browser/chromeos/power/renderer_freezer.cc b/chrome/browser/chromeos/power/renderer_freezer.cc
index 05d4314bf7d3f1e038a831020e49f7e6e507fa8c..187618c15a1af26c982c4932ce6de4369bca0407 100644
--- a/chrome/browser/chromeos/power/renderer_freezer.cc
+++ b/chrome/browser/chromeos/power/renderer_freezer.cc
@@ -148,11 +148,14 @@ void RendererFreezer::OnScreenLockStateChanged(chromeos::ScreenLocker* locker,
   // 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);
+    // |web_contents| is null when using views-based login/lock screen.
+    // TODO(jdufault): Remove this code after webui login/lock is gone. See
+    // crbug.com/719015.
+    content::WebContents* web_contents = locker->delegate()->GetWebContents();
+    if (web_contents) {
+      delegate_->SetShouldFreezeRenderer(
+          web_contents->GetRenderProcessHost()->GetHandle(), false);
+    }
   }
 }