Add sampling profiler

This adds a sampling profiler thread that runs every so often, gathering
profiling data and writing the results to a file in /data/data (specific to
app running).  The intention is to use these files as input to the compiler
so that it can determine the best methods to compile.

Bug: 11539952
Change-Id: I0bfbb4146fb7966673c792f017ffac8107b6272d
diff --git a/runtime/thread_list.cc b/runtime/thread_list.cc
index aed8c77..8bf099b 100644
--- a/runtime/thread_list.cc
+++ b/runtime/thread_list.cc
@@ -211,7 +211,7 @@
       if (thread != self) {
         while (true) {
           if (thread->RequestCheckpoint(checkpoint_function)) {
-            // This thread will run it's checkpoint some time in the near future.
+            // This thread will run its checkpoint some time in the near future.
             count++;
             break;
           } else {