[metrics] Add ClassLoadingTotalTime counter

This keeps track of how much time we spend in the class loading
process.

Testing instructions:

   adb shell setprop dalvik.vm.metrics.write-to-log true
   adb shell stop && adb shell start
   adb logcat -e "ART internal metrics"

Observer ClassLoadingTotalTime in internal metrics report. Example:

    *** ART internal metrics ***
      Metadata:
        timestamp_since_start_ms: 34555
        session_id: 2710488913234081424
        uid: 10065
        compilation_reason: Unknown
        compiler_filter: (unspecified)
      Metrics:
        ClassLoadingTotalTime: count = 120959
        ClassVerificationTotalTime: count = 216121
        JitMethodCompileTime: range = 0...1000000, buckets: 4482,10,2,3
    *** Done dumping ART internal metrics ***

Bug: 177591870
Test: Manual, see above
Change-Id: I24f0c94ab6af5e6cd9b0dc32122f2905c36cf3b7
3 files changed