content: Add out-of-line copy ctors for complex classes.

content/common/gpu/media/vt_video_decode_accelerator_mac.cc

Index: content/common/gpu/media/vt_video_decode_accelerator_mac.cc
diff --git a/content/common/gpu/media/vt_video_decode_accelerator_mac.cc b/content/common/gpu/media/vt_video_decode_accelerator_mac.cc
index f8e0c59953dc640d59334e1e610dfc42ba4934f7..baea1bca140cf19e9c80ad1fe9469133d5b3db48 100644
--- a/content/common/gpu/media/vt_video_decode_accelerator_mac.cc
+++ b/content/common/gpu/media/vt_video_decode_accelerator_mac.cc
@@ -250,6 +250,8 @@ static void OutputThunk(
 VTVideoDecodeAccelerator::Task::Task(TaskType type) : type(type) {
 }
 
+VTVideoDecodeAccelerator::Task::Task(const Task& other) = default;
+
 VTVideoDecodeAccelerator::Task::~Task() {
 }