Restore switch kDisableWebRtcHWEncoding

content/browser/gpu/gpu_data_manager_impl_private.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/gpu/gpu_data_manager_impl_private.h"
 
 #include <algorithm>
 #include <iterator>
 #include <memory>
 #include <utility>
@@ skipping 759 matching lines @@
 
 #if defined(OS_WIN)
   if (IsFeatureBlacklisted(gpu::GPU_FEATURE_TYPE_ACCELERATED_VPX_DECODE) &&
       gpu_preferences) {
     gpu_preferences->enable_accelerated_vpx_decode =
         gpu::GpuPreferences::VPX_VENDOR_NONE;
   }
 #endif
 
 #if BUILDFLAG(ENABLE_WEBRTC)
   if (IsFeatureBlacklisted(gpu::GPU_FEATURE_TYPE_ACCELERATED_VIDEO_ENCODE) &&

[Pawel Osciak, 2017/01/11 09:55:35]

Sorry, I'm confused by the intended logic of this block.

The original logic was to append kDisableWebRtcHWEncoding if encoding was
blacklisted, but the kDisableWebRtcHWEncoding switch was not on commandline
(https://chromium.googlesource.com/chromium/src/+blame/71d41b68d19128f43405820...).

Now, unless I'm misreading something, it seems that we'll only append
kDisableWebRtcHWEncoding if kDisableWebRtcHWVP8Encoding is not on commandline.
However, if kDisableWebRtcHWVP8Encoding is on commandline, then we won't append
kDisableWebRtcHWEncoding regardless of anything else?

Could you explain the intention of the whole block and add comments please?

[braveyao, 2017/01/11 20:46:06]

First of all, now the blacklist is temporarily for blacklisting HW VP8 only on
Android (in the past it will blacklist all HW codec on Android). 
And on Android, generally you can't append commandline flag by clicking App icon
to launch it.

So the logic here is mainly to append the switch to disable HW VP8 on Android.
And then set gpu_preferences or append kDisableWebRtcHWEncoding depending on HW
H264 status.

And I'm preparing to remove the blacklist soon to enable HW VP8 for
mediaRecording only on Android (no WebRTC yet).

-      !command_line->HasSwitch(switches::kDisableWebRtcHWVP8Encoding) &&
-      !base::FeatureList::IsEnabled(features::kWebRtcHWH264Encoding)) {
-    if (gpu_preferences) {
-      gpu_preferences->disable_web_rtc_hw_encoding = true;
-    } else {
-      command_line->AppendSwitch(switches::kDisableWebRtcHWVP8Encoding);
+      !command_line->HasSwitch(switches::kDisableWebRtcHWVP8Encoding)) {
+    command_line->AppendSwitch(switches::kDisableWebRtcHWVP8Encoding);
+
+    if (!base::FeatureList::IsEnabled(features::kWebRtcHWH264Encoding)) {
+      if (gpu_preferences) {
+        gpu_preferences->disable_web_rtc_hw_encoding = true;
+      } else if (!command_line->HasSwitch(switches::kDisableWebRtcHWEncoding)) {
+        command_line->AppendSwitch(switches::kDisableWebRtcHWEncoding);
+      }
     }
   }
 #endif
 
   if (gpu_preferences) { // enable_es3_apis
     bool blacklisted = IsFeatureBlacklisted(gpu::GPU_FEATURE_TYPE_WEBGL2);
     bool enabled = base::CommandLine::ForCurrentProcess()->HasSwitch(
         switches::kEnableES3APIs);
     bool disabled = base::CommandLine::ForCurrentProcess()->HasSwitch(
         switches::kDisableES3APIs);
@@ skipping 534 matching lines @@
   gpu_info_.context_info_state = gpu::kCollectInfoFatalFailure;
 #if defined(OS_WIN)
   gpu_info_.dx_diagnostics_info_state = gpu::kCollectInfoFatalFailure;
 #endif
   complete_gpu_info_already_requested_ = true;
   // Some observers might be waiting.
   NotifyGpuInfoUpdate();
 }
 
 }  // namespace content