MIPS: Start using OStreams.

src/mips/code-stubs-mips.cc

Index: src/mips/code-stubs-mips.cc
diff --git a/src/mips/code-stubs-mips.cc b/src/mips/code-stubs-mips.cc
index 144df40b2619ffb745f55352baedb47639cfd0a5..68d81bbfc74cc75d4cd7da8cf2c2df33d9f3878e 100644
--- a/src/mips/code-stubs-mips.cc
+++ b/src/mips/code-stubs-mips.cc
@@ -418,8 +418,8 @@ class ConvertToDoubleStub : public PlatformCodeStub {
   class ModeBits: public BitField<OverwriteMode, 0, 2> {};
   class OpBits: public BitField<Token::Value, 2, 14> {};
 
-  Major MajorKey() { return ConvertToDouble; }
-  int MinorKey() {
+  Major MajorKey() const { return ConvertToDouble; }
+  int MinorKey() const {
     // Encode the parameters in a unique 16 bit value.
     return  result1_.code() +
            (result2_.code() << 4) +