Using histograms for timing statistics.

  Histogram class and test cases added.
  Modified make file to add test cases and class file.
  Added a guard to avoid race condition in Cumulative logger that
  was possible race between Addlogger and Dump() functions.

Change-Id: I060a0d65648c7120963856624e7008c0aa681eb7
diff --git a/build/Android.common.mk b/build/Android.common.mk
index f613399..8b64519 100644
--- a/build/Android.common.mk
+++ b/build/Android.common.mk
@@ -144,6 +144,7 @@
 	src/base/mutex.cc \
 	src/base/stringpiece.cc \
 	src/base/stringprintf.cc \
+        src/base/timing_logger.cc \
 	src/base/unix_file/fd_file.cc \
 	src/base/unix_file/mapped_file.cc \
 	src/base/unix_file/null_file.cc \
@@ -250,7 +251,6 @@
 	src/thread.cc \
 	src/thread_list.cc \
 	src/thread_pool.cc \
-        src/timing_logger.cc \
 	src/trace.cc \
 	src/utf.cc \
 	src/utils.cc \
@@ -383,6 +383,7 @@
 
 TEST_COMMON_SRC_FILES := \
 	src/barrier_test.cc \
+	src/base/histogram_test.cc \
 	src/base/mutex_test.cc \
 	src/base/unix_file/fd_file_test.cc \
 	src/base/unix_file/mapped_file_test.cc \