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 5e79281b72d553a27f12678c037eee3cc0e1bb5e..5f93ce4fcbfd9d3dcd798aec52e566ba3c3bf059 100644
--- a/gpu/command_buffer/service/texture_manager.cc
+++ b/gpu/command_buffer/service/texture_manager.cc
@@ -404,6 +404,8 @@ Texture::FaceInfo::FaceInfo()
     : num_mip_levels(0) {
 }
 
+Texture::FaceInfo::FaceInfo(const FaceInfo& other) = default;
+
 Texture::FaceInfo::~FaceInfo() {
 }