Clarify resolution change behaviors of video capture devices

content/browser/media/capture/desktop_capture_device.cc

 // Copyright (c) 2013 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/desktop_capture_device.h"
 
 #include "base/bind.h"
 #include "base/location.h"
 #include "base/logging.h"
 #include "base/metrics/histogram.h"
@@ skipping 297 matching lines @@
 void DesktopCaptureDevice::Core::RefreshCaptureFormat(
     const webrtc::DesktopSize& frame_size) {
   if (previous_frame_size_.equals(frame_size))
     return;
 
   // Clear the output frame, if any, since it will either need resizing, or
   // clearing of stale data in letterbox areas, anyway.
   output_frame_.reset();
 
   if (previous_frame_size_.is_empty() ||
-      requested_params_.allow_resolution_change) {
+      requested_params_.resolution_change_policy ==
+      media::RESOLUTION_POLICY_DYNAMIC_WITHIN_LIMIT) {
     // If this is the first frame, or the receiver supports variable resolution
     // then determine the output size by treating the requested width & height
     // as maxima.
     if (frame_size.width() >
             requested_params_.requested_format.frame_size.width() ||
         frame_size.height() >
             requested_params_.requested_format.frame_size.height()) {
       output_rect_ = ComputeLetterboxRect(
           webrtc::DesktopSize(
               requested_params_.requested_format.frame_size.width(),
@@ skipping 144 matching lines @@
 #else
   base::MessageLoop::Type thread_type = base::MessageLoop::TYPE_DEFAULT;
 #endif
 
   thread_.StartWithOptions(base::Thread::Options(thread_type, 0));
 
   core_.reset(new Core(thread_.message_loop_proxy(), capturer.Pass(), type));
 }
 
 }  // namespace content