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

gpu/command_buffer/service/texture_manager.cc

Index: gpu/command_buffer/service/texture_manager.cc
diff --git a/gpu/command_buffer/service/texture_manager.cc b/gpu/command_buffer/service/texture_manager.cc
index eaad260215b4718aa76dede9edeec2d1a3ca9eb7..26b7705322f0575960462c54a28d3c599e4a734c 100644
--- a/gpu/command_buffer/service/texture_manager.cc
+++ b/gpu/command_buffer/service/texture_manager.cc
@@ -403,6 +403,8 @@ Texture::FaceInfo::FaceInfo()
     : num_mip_levels(0) {
 }
 
+Texture::FaceInfo::FaceInfo(const FaceInfo& other) = default;
+
 Texture::FaceInfo::~FaceInfo() {
 }