Support profiling based on linux kernel performance events.

src/platform-macos.cc

Index: src/platform-macos.cc
diff --git a/src/platform-macos.cc b/src/platform-macos.cc
index 47193de7c40498815767e0c80a417e6a178c1408..91860c2c3a2e6b6ce04a0f27299132a4c65aaecd 100644
--- a/src/platform-macos.cc
+++ b/src/platform-macos.cc
@@ -245,6 +245,10 @@ void OS::LogSharedLibraryAddresses() {
 }
 
 
+void OS::SignalCodeMovingGC() {
+}
+
+
 uint64_t OS::CpuFeaturesImpliedByPlatform() {
   // MacOSX requires all these to install so we can assume they are present.
   // These constants are defined by the CPUid instructions.