Enhance SafeStackFrameIterator to avoid triggering assertions in debug mode.

src/mips/frames-mips.cc

Index: src/mips/frames-mips.cc
diff --git a/src/mips/frames-mips.cc b/src/mips/frames-mips.cc
index 0fce3cdd955d08597e53adbebc2d0aa169f91bc5..d6305629951fc34e56d307f941276ae2329fd2a8 100644
--- a/src/mips/frames-mips.cc
+++ b/src/mips/frames-mips.cc
@@ -52,9 +52,7 @@ StackFrame::Type StackFrame::ComputeType(State* state) {
 }
 
 
-StackFrame::Type ExitFrame::GetStateForFramePointer(Address fp, State* state) {
-  if (fp == 0) return NONE;
-  // Compute frame type and stack pointer.
+Address ExitFrame::ComputeStackPointer(Address fp) {
   Address sp = fp + ExitFrameConstants::kSPDisplacement;
   const int offset = ExitFrameConstants::kCodeOffset;
   Object* code = Memory::Object_at(fp + offset);
@@ -62,11 +60,7 @@ StackFrame::Type ExitFrame::GetStateForFramePointer(Address fp, State* state) {
   if (is_debug_exit) {
     sp -= kNumJSCallerSaved * kPointerSize;
   }
-  // Fill in the state.
-  state->sp = sp;
-  state->fp = fp;
-  state->pc_address = reinterpret_cast<Address*>(sp - 1 * kPointerSize);
-  return EXIT;
+  return sp;
 }