Update VideoFramePump to pass un-changed frames to encoders.

remoting/host/fake_desktop_capturer.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 "remoting/host/fake_desktop_capturer.h"
 
 #include "base/bind.h"
 #include "base/logging.h"
 #include "base/memory/ref_counted.h"
 #include "base/time/time.h"
@@ skipping 125 matching lines @@
 
 void FakeDesktopCapturer::Start(Callback* callback) {
   DCHECK(!callback_);
   DCHECK(callback);
   callback_ = callback;
 }
 
 void FakeDesktopCapturer::Capture(const webrtc::DesktopRegion& region) {
   base::Time capture_start_time = base::Time::Now();
   scoped_ptr<webrtc::DesktopFrame> frame = frame_generator_.Run(callback_);
-  frame->set_capture_time_ms(
-      (base::Time::Now() - capture_start_time).InMillisecondsRoundedUp());
+  if (frame) {
+    frame->set_capture_time_ms(
+        (base::Time::Now() - capture_start_time).InMillisecondsRoundedUp());
+  }
   callback_->OnCaptureCompleted(frame.release());
 }
 
 }  // namespace remoting