RFR: 8252526: Remove excessive inclusion of jvmti.h and jvmtiExport.hpp

[Kim Barrett]

On Wed, 11 Nov 2020 00:03:56 GMT, Ioi Lam <iklam at openjdk.org> wrote:

> jvmti.h is included 905 times and jvmtiExport.hpp is included 776 times (out of 971 hotspot .o files). Most of these are unnecessarily included by the following 3 popular header files:
> 
> * javaClasses.hpp: `java_lang_Class::ThreadStatus` (which depends on jvmti.h) this type is rarely used. Move this type to a separate header file. The enum is also changed to an enum class for better type safety.
> * os.hpp: No need to include jvmti.h. Use forward declaration for `struct jvmtiTimerInfo;` instead.
> * thread.hpp: No need to include jvmExport.hpp. Use forward declaration for `JvmtiSampledObjectAllocEventCollector` and `JvmtiVMObjectAllocEventCollector` instead.
> 
> Tested with mach5 tier1-2 and build tiers 3-5.
> 
> Note: Many files are changed, but most of the changes are adding a missing jvmtiExports.hpp.
> 
> Original review thread: https://mail.openjdk.java.net/pipermail/hotspot-runtime-dev/2020-August/041509.html

Nice!

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Marked as reviewed by kbarrett (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/1152