Tweak the "art --perf" helper command.

Enable use of dwarf as frame-pointer unwinding is unreliable.
Set the frequency to 10000 samples per second.

Test: run the tool
Change-Id: I6cc19a674b162e95183d0263cf016cc90372b560
diff --git a/tools/art b/tools/art
index 62df7eb..aebf5a6 100644
--- a/tools/art
+++ b/tools/art
@@ -359,7 +359,7 @@
 fi
 
 if [ "$PERF" != "" ]; then
-  LAUNCH_WRAPPER="perf record -g -o $ANDROID_DATA/perf.data -e cycles:u $LAUNCH_WRAPPER"
+  LAUNCH_WRAPPER="perf record -g --call-graph dwarf -F 10000 -o $ANDROID_DATA/perf.data -e cycles:u $LAUNCH_WRAPPER"
   EXTRA_OPTIONS+=(-Xcompiler-option --generate-debug-info)
 fi