MIPS: Adding assertions to fast elements conversion.

Port r9875 (97dc1e0e).

BUG=
TEST=

Review URL: http://codereview.chromium.org/8467008
Patch from Gergely Kis <gergely@homejinni.com>.

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@9891 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/mips/codegen-mips.cc

@@ -186,6 +186,10 @@ void ElementsTransitionGenerator::GenerateSmiOnlyToDouble(
 
   // Hole found, store the-hole NaN.
   __ bind(&convert_hole);
+  if (FLAG_debug_code) {
+    __ LoadRoot(at, Heap::kTheHoleValueRootIndex);
+    __ Assert(eq, "object found in smi-only array", at, Operand(t5));
+  }
   __ sw(t0, MemOperand(t3));  // mantissa
   __ sw(t1, MemOperand(t3, kIntSize));  // exponent
   __ Addu(t3, t3, kDoubleSize);