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

media/video/video_decode_accelerator.cc

Index: media/video/video_decode_accelerator.cc
diff --git a/media/video/video_decode_accelerator.cc b/media/video/video_decode_accelerator.cc
index 0d3887d02133e6a3381a3e5afa0f15504124c07c..4275d5fec83c744382fa20a99a2aebdd643162b8 100644
--- a/media/video/video_decode_accelerator.cc
+++ b/media/video/video_decode_accelerator.cc
@@ -51,6 +51,9 @@ VideoDecodeAccelerator::SupportedProfile::~SupportedProfile() {}
 
 VideoDecodeAccelerator::Capabilities::Capabilities() : flags(NO_FLAGS) {}
 
+VideoDecodeAccelerator::Capabilities::Capabilities(const Capabilities& other) =
+    default;
+
 VideoDecodeAccelerator::Capabilities::~Capabilities() {}
 
 std::string VideoDecodeAccelerator::Capabilities::AsHumanReadableString()