Implements a new API to set a function entry hook for profiling.

src/x64/full-codegen-x64.cc

Index: src/x64/full-codegen-x64.cc
diff --git a/src/x64/full-codegen-x64.cc b/src/x64/full-codegen-x64.cc
index 050c0d657ef91fcfc476c870f3d3ce0b17241569..6aef7267807456a12dba9f5f7f3b89d52de14ae8 100644
--- a/src/x64/full-codegen-x64.cc
+++ b/src/x64/full-codegen-x64.cc
@@ -130,6 +130,12 @@ void FullCodeGenerator::Generate() {
   }
 #endif
 
+  const FunctionEntryHook* hook_location = V8::GetFunctionEntryHookLocation();
+  if (*hook_location != NULL) {
+    ProfileEntryHookStub stub;
+    __ CallStub(&stub);
+  }
+
   // Strict mode functions and builtins need to replace the receiver
   // with undefined when called as functions (without an explicit
   // receiver object). rcx is zero for method calls and non-zero for