Add thread suspend histogram

Helps measure time to suspend.
Example output (maps after a few seconds):
suspend all histogram:  Sum: 2.806ms 99% C.I. 2us-1090.560us Avg: 43.843us Max: 1126us

Change-Id: I7bd9dd3b401fb3e3059e8718556d60910e541611
diff --git a/runtime/base/histogram.h b/runtime/base/histogram.h
index 1e12be8..78f6e1c 100644
--- a/runtime/base/histogram.h
+++ b/runtime/base/histogram.h
@@ -46,6 +46,7 @@
   // This is the expected constructor when creating new Histograms.
   Histogram(const char* name, Value initial_bucket_width, size_t max_buckets = 100);
   void AddValue(Value);
+  void AdjustAndAddValue(Value);  // Add a value after dividing it by kAdjust.
   // Builds the cumulative distribution function from the frequency data.
   // Accumulative summation of frequencies.
   // cumulative_freq[i] = sum(frequency[j] : 0 < j < i )