The jhat tool has been removed. jhat hprof file parser/validator
are needed for tests. The old packages for jhat were moved here:
com.sun.tools.hat.internal.model -> jdk.test.lib.hprof.model
com.sun.tools.hat.internal.parser -> jdk.test.lib.hprof.parser
com.sun.tools.hat.internal.util -> jdk.test.lib.hprof.util
 
jhat was added in JDK 6 and its original implementation was from 
java.net HAT project [1]. jhat is an experimental, unsupported tool. 
There hasn't been much update to jhat tool in the JDK. In addition, 
there are several better heap dump visualizer/analyzer emerged since 
JDK 5/6 serviceability support.

[1] https://java.net/projects/hat
