Add asserts to ensure that we:

src/macro-assembler.h

Index: src/macro-assembler.h
===================================================================
--- src/macro-assembler.h	(revision 9277)
+++ src/macro-assembler.h	(working copy)
@@ -93,6 +93,63 @@
 namespace v8 {
 namespace internal {
 
+class FrameScope {
+ public:
+  explicit FrameScope(MacroAssembler* masm, StackFrame::Type type)
+      : masm_(masm), type_(type) {
+    ASSERT(!masm->has_frame());
+    masm->set_has_frame(true);
+    if (type != StackFrame::MANUAL && type_ != StackFrame::NONE) {
+      masm->EnterFrame(type);
+    }
+  }
+
+  ~FrameScope() {
+    if (type_ != StackFrame::MANUAL && type_ != StackFrame::NONE) {
+      masm_->LeaveFrame(type_);
+    }
+    masm_->set_has_frame(false);
+  }
+
+  // Normally we generate the leave-frame code when this object goes
+  // out of scope.  Sometimes we may need to generate the code somewhere else
+  // in addition.  Calling this will achieve that, but the object stays in
+  // scope, the MacroAssembler is still marked as being in a frame scope, and
+  // the code will be generated again when it goes out of scope.
+  void GenerateLeaveFrame() {
+    masm_->LeaveFrame(type_);
+  }
+
+ private:
+  MacroAssembler* masm_;
+  StackFrame::Type type_;
+};
+
+
+class AllowExternalCallThatCantCauseGC: public FrameScope {
+ public:
+  explicit AllowExternalCallThatCantCauseGC(MacroAssembler* masm)
+      : FrameScope(masm, StackFrame::NONE) { }
+};
+
+
+class NoCurrentFrameScope {
+ public:
+  explicit NoCurrentFrameScope(MacroAssembler* masm)
+      : masm_(masm), saved_(masm->has_frame()) {
+    masm->set_has_frame(false);
+  }
+
+  ~NoCurrentFrameScope() {
+    masm_->set_has_frame(saved_);
+  }
+
+ private:
+  MacroAssembler* masm_;
+  bool saved_;
+};
+
+
 // Support for "structured" code comments.
 #ifdef DEBUG