Fix an overflow in on-stack replacement spill-slot allocation for Crankshaft.

src/lithium.h

Index: src/lithium.h
diff --git a/src/lithium.h b/src/lithium.h
index 3f8a6ba4d2da30bc424c374e52da36e63a4ec7ad..6010b777ed130d5e23ae34e4b886c62e58d753dc 100644
--- a/src/lithium.h
+++ b/src/lithium.h
@@ -144,7 +144,8 @@ class LUnallocated: public LOperand {
   };
 
   static const int kMaxVirtualRegisters = 1 << (kVirtualRegisterWidth + 1);
-  static const int kMaxFixedIndices = 128;
+  static const int kMaxFixedIndex = 63;
+  static const int kMinFixedIndex = -64;
 
   bool HasIgnorePolicy() const { return policy() == IGNORE; }
   bool HasNoPolicy() const { return policy() == NONE; }