Add ActivationFrame_GetFramePointer method and test.

runtime/vm/debugger_api_impl.cc

Index: runtime/vm/debugger_api_impl.cc
diff --git a/runtime/vm/debugger_api_impl.cc b/runtime/vm/debugger_api_impl.cc
index 62d99a4dc69c3191c58e7124e2e4fd162bcc91a7..f5c0a6b2022835e9e59c10a2cd75d4159034e2c1 100644
--- a/runtime/vm/debugger_api_impl.cc
+++ b/runtime/vm/debugger_api_impl.cc
@@ -308,6 +308,19 @@ DART_EXPORT Dart_Handle Dart_ActivationFrameGetLocation(
   return Api::Success();
 }
 
+DART_EXPORT Dart_Handle Dart_ActivationFrameGetFramePointer(
+                            Dart_ActivationFrame activation_frame,
+                            uintptr_t* frame_pointer) {
+  Isolate* isolate = Isolate::Current();
+  DARTSCOPE(isolate);
+  CHECK_AND_CAST(ActivationFrame, frame, activation_frame);
+
+  if (frame_pointer != NULL) {
+    *frame_pointer = static_cast<uintptr_t>(frame->fp());

[hausner, 2014/09/05 19:16:59]

This is fine. How does it play with the V8 side of your change where you mask
the top bits so the FP fits into 53 bits? if the stack is in the top of the
address space, this would not work. (Yes, only 48 bit are used on x64, but the
only requirement is that bits 48..63 are either all 0 or all 1. So,
0xffffffff'ffff0000 for example is a valid address.

[Jacob, 2014/09/05 20:12:25]

In blink I truncate Dart stack frame values before storing them as doubles to
make it consistent with V8. I thought it was cleaner that way as there is no
need for Dart to know about a hack that is there just to work around the lack of
a 64bit int type in JS.

+  }
+  return Api::Success();
+}
+
 
 DART_EXPORT Dart_Handle Dart_GetFunctionOrigin(Dart_Handle function_in) {
   Isolate* isolate = Isolate::Current();