Protect frame_adapter_ with a lock in WebrtcVideoFrameAdapter

Bug: webrtc:11485
Change-Id: I843b0babbcc5ac1169ab09ea957d5df02bc52f29
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2449333
Auto-Submit: Ilya Nikolaevskiy <ilnik@chromium.org>
Reviewed-by: Henrik Boström <hbos@chromium.org>
Commit-Queue: Ilya Nikolaevskiy <ilnik@chromium.org>
Cr-Commit-Position: refs/heads/master@{#813707}

third_party/blink/renderer/platform/webrtc/webrtc_video_frame_adapter.cc

@@ -244,6 +244,7 @@ WebRtcVideoFrameAdapter::CreateFrameAdapter() const {
 
 rtc::scoped_refptr<webrtc::I420BufferInterface>
 WebRtcVideoFrameAdapter::ToI420() {
+  base::AutoLock auto_lock(adapter_lock_);
   if (!frame_adapter_) {
     frame_adapter_ = CreateFrameAdapter();
   }
@@ -251,6 +252,7 @@ WebRtcVideoFrameAdapter::ToI420() {
 }
 
 const webrtc::I420BufferInterface* WebRtcVideoFrameAdapter::GetI420() const {
+  base::AutoLock auto_lock(adapter_lock_);
   if (!frame_adapter_) {
     frame_adapter_ = CreateFrameAdapter();
   }

third_party/blink/renderer/platform/webrtc/webrtc_video_frame_adapter.h

@@ -7,6 +7,7 @@
 
 #include <stdint.h>
 
+#include "base/synchronization/lock.h"
 #include "media/base/video_frame.h"
 #include "third_party/blink/renderer/platform/platform_export.h"
 #include "third_party/webrtc/api/video/video_frame_buffer.h"
@@ -40,9 +41,12 @@ class PLATFORM_EXPORT WebRtcVideoFrameAdapter
 
   rtc::scoped_refptr<webrtc::I420BufferInterface> CreateFrameAdapter() const;
 
+  mutable base::Lock adapter_lock_;
+
   // Used to cache result of CreateFrameAdapter. Which is called from const
   // GetI420().
-  mutable rtc::scoped_refptr<webrtc::I420BufferInterface> frame_adapter_;
+  mutable rtc::scoped_refptr<webrtc::I420BufferInterface> frame_adapter_
+      GUARDED_BY(adapter_lock_);
 
   scoped_refptr<media::VideoFrame> frame_;