MIPS: Introduce LanguageMode, drop StrictMode.

src/compiler/mips64/code-generator-mips64.cc

Index: src/compiler/mips64/code-generator-mips64.cc
diff --git a/src/compiler/mips64/code-generator-mips64.cc b/src/compiler/mips64/code-generator-mips64.cc
index a3f47a1d78c2b1a2a375b35dbd3236a59ef62c85..1ee4f2507606d1c1a78a41afc07ec97eafaedc5a 100644
--- a/src/compiler/mips64/code-generator-mips64.cc
+++ b/src/compiler/mips64/code-generator-mips64.cc
@@ -1061,7 +1061,7 @@ void CodeGenerator::AssemblePrologue() {
     // global proxy when called as functions (without an explicit receiver
     // object).
     // TODO(mstarzinger/verwaest): Should this be moved back into the CallIC?
-    if (info->strict_mode() == SLOPPY && !info->is_native()) {
+    if (is_sloppy(info->language_mode()) && !info->is_native()) {
       Label ok;
       // +2 for return address and saved frame pointer.
       int receiver_slot = info->scope()->num_parameters() + 2;