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

gpu/command_buffer/service/vertex_attrib_manager.cc

Index: gpu/command_buffer/service/vertex_attrib_manager.cc
diff --git a/gpu/command_buffer/service/vertex_attrib_manager.cc b/gpu/command_buffer/service/vertex_attrib_manager.cc
index 66986450334f1c58658280463ba10d1bf920fd1c..7ec12e8b308e5bdb8b89f5142c6bb53950b7c22c 100644
--- a/gpu/command_buffer/service/vertex_attrib_manager.cc
+++ b/gpu/command_buffer/service/vertex_attrib_manager.cc
@@ -41,6 +41,8 @@ VertexAttrib::VertexAttrib()
       list_(NULL) {
 }
 
+VertexAttrib::VertexAttrib(const VertexAttrib& other) = default;
+
 VertexAttrib::~VertexAttrib() {
 }