Fix nullptr access in CursorRendererAura::SnapshotCursorState.

content/browser/media/capture/cursor_renderer_aura.cc

 // Copyright (c) 2015 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 "content/browser/media/capture/cursor_renderer_aura.h"
 
 #include <stdint.h>
 
 #include <algorithm>
 #include <cmath>
@@ skipping 91 matching lines @@
   // cursor when the window is active.
   if (!window_->IsRootWindow()) {
     aura::client::ActivationClient* activation_client =
         aura::client::GetActivationClient(window_->GetRootWindow());
     if (!activation_client) {
       DVLOG(2) << "Assume window inactive with invalid activation_client";
       Clear();
       return false;
     }
     aura::Window* active_window = activation_client->GetActiveWindow();
+    if (!active_window) {
+      DVLOG(2) << "Skipping update as there is no active window";
+      Clear();
+      return false;
+    }
     if (!active_window->Contains(window_)) {
       // Return early if the target window is not active.
       DVLOG(2) << "Skipping update on an inactive window";
       Clear();
       return false;
     }
   }
 
   if (cursor_display_setting_ == kCursorEnabledOnMouseMovement) {
     if (cursor_displayed_) {
@@ skipping 124 matching lines @@
 
 void CursorRendererAura::OnWindowDestroying(aura::Window* window) {
   DCHECK_EQ(window_, window);
   if (cursor_display_setting_ == kCursorEnabledOnMouseMovement)
     window_->RemovePreTargetHandler(this);
   window_->RemoveObserver(this);
   window_ = nullptr;
 }
 
 }  // namespace content