Also time external callbacks from generated code.

src/x64/macro-assembler-x64.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 702 matching lines @@
       ExternalReference::scheduled_exception_address(isolate());
 
   // Allocate HandleScope in callee-save registers.
   Register prev_next_address_reg = r14;
   Register prev_limit_reg = rbx;
   Register base_reg = r15;
   movq(base_reg, next_address);
   movq(prev_next_address_reg, Operand(base_reg, kNextOffset));
   movq(prev_limit_reg, Operand(base_reg, kLimitOffset));
   addl(Operand(base_reg, kLevelOffset), Immediate(1));
+
+  if (FLAG_log_timer_events) {
+    FrameScope frame(this, StackFrame::MANUAL);
+    PushSafepointRegisters();
+    PrepareCallCFunction(0);
+    CallCFunction(ExternalReference::log_enter_external_function(isolate()), 0);
+    PopSafepointRegisters();
+  }
+
   // Call the api function!
   movq(rax, reinterpret_cast<int64_t>(function_address),
        RelocInfo::RUNTIME_ENTRY);
   call(rax);
 
+  if (FLAG_log_timer_events) {
+    FrameScope frame(this, StackFrame::MANUAL);
+    PushSafepointRegisters();
+    PrepareCallCFunction(0);
+    CallCFunction(ExternalReference::log_leave_external_function(isolate()), 0);
+    PopSafepointRegisters();
+  }
+
 #if defined(_WIN64) && !defined(__MINGW64__)
   // rax keeps a pointer to v8::Handle, unpack it.
   movq(rax, Operand(rax, 0));
 #endif
   // Check if the result handle holds 0.
   testq(rax, rax);
   j(zero, &empty_result);
   // It was non-zero.  Dereference to get the result value.
   movq(rax, Operand(rax, 0));
   bind(&prologue);
@@ skipping 3830 matching lines @@
 
   movq(rcx, FieldOperand(rbx, Map::kPrototypeOffset));
   cmpq(rcx, null_value);
   j(not_equal, &next);
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64