Mac zero copy capture: Enable IOSurfaces behind flag

Add a AVFoundationCaptureV2ZeroCopy feature flag to control exporting
IOSurfaces directly out of VideoCaptureDeviceAVFoundation. This flag
will do nothing unless AVFoundationCaptureV2 is also specified.

Bug: 1125879
Change-Id: If18c797ad2cdb6abab73679df7ef9b150fc39f61
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2425084Reviewed-by: Dan Sanders <sandersd@chromium.org>
Reviewed-by: Markus Handell <handellm@google.com>
Commit-Queue: Markus Handell <handellm@google.com>
Cr-Commit-Position: refs/heads/master@{#809725}

media/base/media_switches.cc

@@ -664,6 +664,11 @@ const base::Feature MEDIA_EXPORT kMediaFoundationVP8Decoding{
 const base::Feature MEDIA_EXPORT kAVFoundationCaptureV2{
     "AVFoundationCaptureV2", base::FEATURE_DISABLED_BY_DEFAULT};
 
+// Controls whether or not the V2 capturer exports IOSurfaces for zero-copy.
+// This feature only has any effect if kAVFoundationCaptureV2 is also enabled.
+const base::Feature MEDIA_EXPORT kAVFoundationCaptureV2ZeroCopy{
+    "AVFoundationCaptureV2ZeroCopy", base::FEATURE_ENABLED_BY_DEFAULT};
+
 const base::Feature MEDIA_EXPORT kVideoToolboxVp9Decoding{
     "VideoToolboxVp9Decoding", base::FEATURE_DISABLED_BY_DEFAULT};
 #endif  // defined(OS_MAC)

media/base/media_switches.h

@@ -226,6 +226,7 @@ MEDIA_EXPORT extern const base::Feature kMediaFoundationVP8Decoding;
 
 #if defined(OS_MAC)
 MEDIA_EXPORT extern const base::Feature kAVFoundationCaptureV2;
+MEDIA_EXPORT extern const base::Feature kAVFoundationCaptureV2ZeroCopy;
 MEDIA_EXPORT extern const base::Feature kVideoToolboxVp9Decoding;
 #endif
 

media/capture/video/mac/video_capture_device_avfoundation_mac.mm

@@ -17,6 +17,7 @@
 #include "base/sequenced_task_runner.h"
 #include "base/strings/string_util.h"
 #include "base/strings/sys_string_conversions.h"
+#include "media/base/media_switches.h"
 #include "media/base/timestamp_constants.h"
 #include "media/base/video_types.h"
 #import "media/capture/video/mac/video_capture_device_avfoundation_utils_mac.h"
@@ -654,9 +655,8 @@ AVCaptureDeviceFormat* FindBestCaptureFormat(
     DCHECK_EQ(pixelBufferPixelFormat, sampleBufferPixelFormat);
 
     // First preference is to use an NV12 IOSurface as a GpuMemoryBuffer.
-    // TODO(https://crbug.com/1125879): This path cannot be used in software
-    // mode yet, and so it cannot be enabled yet.
-    constexpr bool kEnableGpuMemoryBuffers = false;
+    static const bool kEnableGpuMemoryBuffers =
+        base::FeatureList::IsEnabled(media::kAVFoundationCaptureV2ZeroCopy);
     if (kEnableGpuMemoryBuffers) {
       IOSurfaceRef ioSurface = CVPixelBufferGetIOSurface(pixelBuffer);
       if (ioSurface && videoPixelFormat == media::PIXEL_FORMAT_NV12) {