Fix potential unsafe access to VCMTimestampMap::data

The access to |_timestampMap| was guarded by a lock but
not the access to the data pointer stored in |_timestampMap|.
There was a potential race condition if new data was added
in VCMGenericDecoder::Decode() while the data pointer
retrieved from _timestampMap.Pop() was being used in
VCMDecodedFrameCallback::Decoded().

This CL moves the storage of data to within |_timestampMap|,
instead of being a pointer so that it's guarded by the same
lock.

Bug: webrtc:11229
Change-Id: I3f2afb568ed724db5719d508a73de402c4531dec
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/209361
Commit-Queue: Johannes Kron <kron@webrtc.org>
Reviewed-by: Ilya Nikolaevskiy <ilnik@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#33374}
diff --git a/modules/video_coding/timestamp_map.h b/modules/video_coding/timestamp_map.h
index cfa1257..86ce55b 100644
--- a/modules/video_coding/timestamp_map.h
+++ b/modules/video_coding/timestamp_map.h
@@ -13,23 +13,41 @@
 
 #include <memory>
 
+#include "absl/types/optional.h"
+#include "api/rtp_packet_infos.h"
+#include "api/units/timestamp.h"
+#include "api/video/encoded_image.h"
+#include "api/video/video_content_type.h"
+#include "api/video/video_rotation.h"
+#include "api/video/video_timing.h"
+
 namespace webrtc {
 
-struct VCMFrameInformation;
+struct VCMFrameInformation {
+  int64_t renderTimeMs;
+  absl::optional<Timestamp> decodeStart;
+  void* userData;
+  VideoRotation rotation;
+  VideoContentType content_type;
+  EncodedImage::Timing timing;
+  int64_t ntp_time_ms;
+  RtpPacketInfos packet_infos;
+  // ColorSpace is not stored here, as it might be modified by decoders.
+};
 
 class VCMTimestampMap {
  public:
   explicit VCMTimestampMap(size_t capacity);
   ~VCMTimestampMap();
 
-  void Add(uint32_t timestamp, VCMFrameInformation* data);
-  VCMFrameInformation* Pop(uint32_t timestamp);
+  void Add(uint32_t timestamp, const VCMFrameInformation& data);
+  absl::optional<VCMFrameInformation> Pop(uint32_t timestamp);
   size_t Size() const;
 
  private:
   struct TimestampDataTuple {
     uint32_t timestamp;
-    VCMFrameInformation* data;
+    VCMFrameInformation data;
   };
   bool IsEmpty() const;