Make standalone D8 trace to single hydrogen.cfg file.

src/d8.cc

Index: src/d8.cc
diff --git a/src/d8.cc b/src/d8.cc
index 5343174d1741489877f29ecfc9885fa568fc506f..1efe2ae0b407958fc4b2e0632e7597f4ae215fe2 100644
--- a/src/d8.cc
+++ b/src/d8.cc
@@ -1547,11 +1547,12 @@ int Shell::RunMain(Isolate* isolate, int argc, char* argv[]) {
 
 
 #ifdef V8_SHARED
-static void EnableHarmonyTypedArraysViaCommandLine() {
-  int fake_argc = 2;
-  char **fake_argv = new char*[2];
+static void SetStandaloneFlagsViaCommandLine() {
+  int fake_argc = 3;
+  char **fake_argv = new char*[3];
   fake_argv[0] = NULL;
   fake_argv[1] = strdup("--harmony-typed-arrays");
+  fake_argv[2] = strdup("--trace-hydrogen-file=hydrogen.cfg");
   v8::V8::SetFlagsFromCommandLine(&fake_argc, fake_argv, false);
   free(fake_argv[1]);
   delete[] fake_argv;
@@ -1572,8 +1573,9 @@ int Shell::Main(int argc, char* argv[]) {
 #ifndef V8_SHARED
   i::FLAG_harmony_array_buffer = true;
   i::FLAG_harmony_typed_arrays = true;
+  i::FLAG_trace_hydrogen_file = "hydrogen.cfg";
 #else
-  EnableHarmonyTypedArraysViaCommandLine();
+  SetStandaloneFlagsViaCommandLine();
 #endif
   ShellArrayBufferAllocator array_buffer_allocator;
   v8::V8::SetArrayBufferAllocator(&array_buffer_allocator);