Cleanup frame description constant.

src/frames.cc

Index: src/frames.cc
diff --git a/src/frames.cc b/src/frames.cc
index 5aefe066f5ba7cfb9f871718525fad9858a88a8d..723db4ae13c3c6e8da7a173578bd545c6e0ced7b 100644
--- a/src/frames.cc
+++ b/src/frames.cc
@@ -737,6 +737,8 @@ Object* JavaScriptFrame::GetOriginalConstructor() const {
     fp = Memory::Address_at(fp + StandardFrameConstants::kCallerFPOffset);
   }
   DCHECK(IsConstructFrame(fp));
+  STATIC_ASSERT(ConstructFrameConstants::kOriginalConstructorOffset ==
+                StandardFrameConstants::kExpressionsOffset - 2 * kPointerSize);
   return GetExpression(fp, 2);
 }
 
@@ -744,6 +746,8 @@ Object* JavaScriptFrame::GetOriginalConstructor() const {
 int JavaScriptFrame::GetArgumentsLength() const {
   // If there is an arguments adaptor frame get the arguments length from it.
   if (has_adapted_arguments()) {
+    STATIC_ASSERT(ArgumentsAdaptorFrameConstants::kLengthOffset ==
+                  StandardFrameConstants::kExpressionsOffset);
     return Smi::cast(GetExpression(caller_fp(), 0))->value();
   } else {
     return GetNumberOfIncomingArguments();