Fix NotifyStubFailureSaveDoubles generation for ia32.

src/arguments.cc

Index: src/arguments.cc
diff --git a/src/arguments.cc b/src/arguments.cc
index ae06bd081b8b8b5334919b3e4faab53372ca8b1b..205da7c68a69139a3aa05948ed9ffb7ca8bae603 100644
--- a/src/arguments.cc
+++ b/src/arguments.cc
@@ -120,6 +120,7 @@ FOR_EACH_CALLBACK_TABLE_MAPPING_2_VOID_RETURN(WRITE_CALL_2_VOID)
 double ClobberDoubleRegisters(double x1, double x2, double x3, double x4) {
   // TODO(ulan): This clobbers only subset of registers depending on compiler,
   // Rewrite this in assembly to really clobber all registers.
+  // GCC for ia32 uses the FPU and does not touch XMM registers.
   return x1 * 1.01 + x2 * 2.02 + x3 * 3.03 + x4 * 4.04;
 }