In order to compile constant references to method handles and method types, the constant pool structure needs to be able to represent method handle references, and the ldc instruction updated (as it was for Class constants).
This feature completes the role of method handle as a lightweight but dynamic access point to any bytecode operation. Without the ability to perform 'ldc', building a handle to a proposed bytecode level member access is 1-2 orders of magnitude more expensive, requiring a reflective lookup.
For a draft specification, see the package information in the JSR 292 javadoc. It is posted here for review: