Fix crash when view is already deleted

content/browser/media/capture/web_contents_video_capture_device.cc

Index: content/browser/media/capture/web_contents_video_capture_device.cc
diff --git a/content/browser/media/capture/web_contents_video_capture_device.cc b/content/browser/media/capture/web_contents_video_capture_device.cc
index d69a0bc6ce3c8849d25d2cfadca262cac8d13c2d..c2a9090eeba1218deb63ca49939bec49ab202967 100644
--- a/content/browser/media/capture/web_contents_video_capture_device.cc
+++ b/content/browser/media/capture/web_contents_video_capture_device.cc
@@ -443,8 +443,10 @@ ContentCaptureSubscription::ContentCaptureSubscription(
 // TODO(isheriff): Needs implementation on non-aura platforms.
 // https://crbug.com/567735
 #if defined(USE_AURA)
-  window_activity_tracker_.reset(
-      new content::WindowActivityTrackerAura(view->GetNativeView()));
+  if (view) {

[miu, 2015/12/30 00:22:40]

Possible clean-up in future CL: Looks like we should just check the view at the
top of this method and return early if nullptr.  Or, maybe the caller should not
instantiate a ContentCaptureSubscription if the view is null?

[Irfan, 2015/12/30 00:32:12]

I like not instantiating ContentCaptureSubscription when view is null, but I
leave this as-is right now.

+    window_activity_tracker_.reset(
+        new content::WindowActivityTrackerAura(view->GetNativeView()));
+  }
 #endif
   timer_subscriber_.reset(new FrameSubscriber(
       media::VideoCaptureOracle::kTimerPoll, oracle_proxy, &delivery_log_,