Summary
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Constrain constant dynamic bootstrap methods to methods whose first parameter type is `MethodHandles.Lookup`.

Problem
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It's not easy to use existing methods as constant dynamic bootstrap methods. A level of indirection is required, either explicitly or via use of the bootstrap method `ConstantBootstraps.invoke` to drop the first three arguments of lookup, name, and type. While this change does not address that problem it will ensure the problem can be addressed in a future release without affecting compatibility of existing constant dynamic bootstrap methods.

Solution
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Constrain constant dynamic bootstrap methods to methods whose first parameter type is `MethodHandles.Lookup`. 

Specification
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The VM specification will require updating, tracked by JDK-8199051. The `java/lang/invoke/package-html.java` has been updated (see attached).