Add libfieldcount jvmti agent

This agent is useful for extracting information about the contents of
fields and measuring the memory impact of CLs based on the different
counts of various fields.

Test: manual
Test: ./test/run-test --host --dev --interpreter --runtime-option -Xopaque-jni-ids:true --64 --with-agent $ANDROID_HOST_OUT/lib64/libfieldcountd.so=Ljava/lang/Class\;.extData:Ldalvik/system/ClassExt\;,Ldalvik/system/ClassExt\;.jmethodIDs:Ljava/lang/Object\;,Ldalvik/system/ClassExt\;.staticJfieldIDs:Ljava/lang/Object\;,Ldalvik/system/ClassExt\;.instanceJfieldIDs:Ljava/lang/Object\; 001-HelloWorld
Bug: 134162467
Change-Id: I21cfded08f8d9f7db67a81e2ce88ef7567599d97
3 files changed