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

src/v8.h

Index: src/v8.h
diff --git a/src/v8.h b/src/v8.h
index 67716d8107a6014181d3cbd646e8ae561d8c694c..8c113c864582c828c920ed6a6e8a5c83ef262d10 100644
--- a/src/v8.h
+++ b/src/v8.h
@@ -99,6 +99,10 @@ class V8 : public AllStatic {
   // Support for return-address rewriting profilers.
   static void SetReturnAddressLocationResolver(
       ReturnAddressLocationResolver resolver);
+  // Support for a function entry profiling hook.
+  static void SetFunctionEntryHook(uintptr_t entry_hook);
+  // Returns the current function entry profiling hook if any.
+  static uintptr_t GetFunctionEntryHook();
   // Random number generation support. Not cryptographically safe.
   static uint32_t Random(Context* context);
   // We use random numbers internally in memory allocation and in the