Emit symbol maps for compiled code for use by the Linux perf tool.

runtime/bin/process_linux.cc

Index: runtime/bin/process_linux.cc
diff --git a/runtime/bin/process_linux.cc b/runtime/bin/process_linux.cc
index 5ad97dff7bc6c4ecb418828ea6393b42e17226cd..c834988111101fcd2161173b4c73d53079e2775f 100644
--- a/runtime/bin/process_linux.cc
+++ b/runtime/bin/process_linux.cc
@@ -563,3 +563,8 @@ bool Process::Kill(intptr_t id, int signal) {
 void Process::TerminateExitCodeHandler() {
   ExitCodeHandler::TerminateExitCodeThread();
 }
+
+
+intptr_t Process::CurrentProcessId() {
+  return static_cast<intptr_t>(getpid());
+}