Enhance SafeStackFrameIterator to avoid triggering assertions in debug mode.

src/x64/frames-x64.cc

Index: src/x64/frames-x64.cc
diff --git a/src/x64/frames-x64.cc b/src/x64/frames-x64.cc
index fd265351554002dbfd6eb461eeef544cefad7f61..9c960478aa9d33f4bb1a6ca664a24a6c41d0029a 100644
--- a/src/x64/frames-x64.cc
+++ b/src/x64/frames-x64.cc
@@ -35,18 +35,8 @@ namespace v8 {
 namespace internal {
 
 
-
-
-StackFrame::Type ExitFrame::GetStateForFramePointer(Address fp, State* state) {
-  if (fp == 0) return NONE;
-  // Compute the stack pointer.
-  Address sp = Memory::Address_at(fp + ExitFrameConstants::kSPOffset);
-  // Fill in the state.
-  state->fp = fp;
-  state->sp = sp;
-  state->pc_address = reinterpret_cast<Address*>(sp - 1 * kPointerSize);
-  ASSERT(*state->pc_address != NULL);
-  return EXIT;
+Address ExitFrame::ComputeStackPointer(Address fp) {
+  return Memory::Address_at(fp + ExitFrameConstants::kSPOffset);
 }