[stubs] Remove unused StoreGlobalViaContextStub.

src/mips/interface-descriptors-mips.cc

Index: src/mips/interface-descriptors-mips.cc
diff --git a/src/mips/interface-descriptors-mips.cc b/src/mips/interface-descriptors-mips.cc
index aed41420d6057be4ae5d81c6991dacba079df250..330ba5d49c337d479887cfccfdbf0a87fc902853 100644
--- a/src/mips/interface-descriptors-mips.cc
+++ b/src/mips/interface-descriptors-mips.cc
@@ -44,10 +44,6 @@ const Register StoreTransitionDescriptor::SlotRegister() { return t0; }
 const Register StoreTransitionDescriptor::VectorRegister() { return a3; }
 const Register StoreTransitionDescriptor::MapRegister() { return t1; }
 
-const Register StoreGlobalViaContextDescriptor::SlotRegister() { return a2; }
-const Register StoreGlobalViaContextDescriptor::ValueRegister() { return a0; }
-
-
 const Register StringCompareDescriptor::LeftRegister() { return a1; }
 const Register StringCompareDescriptor::RightRegister() { return a0; }