[compiler] Remove dangerous language mode accessors.

src/crankshaft/hydrogen.cc

Index: src/crankshaft/hydrogen.cc
diff --git a/src/crankshaft/hydrogen.cc b/src/crankshaft/hydrogen.cc
index d16deaba66ad18ac1bc4baec19105b600145f28d..d70b4805e1a66fc045f9612b0721add3d4328f91 100644
--- a/src/crankshaft/hydrogen.cc
+++ b/src/crankshaft/hydrogen.cc
@@ -12266,10 +12266,9 @@ void HOptimizedGraphBuilder::VisitDeclarations(
     Handle<FixedArray> array =
        isolate()->factory()->NewFixedArray(globals_.length(), TENURED);
     for (int i = 0; i < globals_.length(); ++i) array->set(i, *globals_.at(i));
-    int flags =
-        DeclareGlobalsEvalFlag::encode(current_info()->is_eval()) |
-        DeclareGlobalsNativeFlag::encode(current_info()->is_native()) |
-        DeclareGlobalsLanguageMode::encode(current_info()->language_mode());
+    int flags = DeclareGlobalsEvalFlag::encode(current_info()->is_eval()) |
+                DeclareGlobalsNativeFlag::encode(current_info()->is_native()) |
+                DeclareGlobalsLanguageMode::encode(function_language_mode());
     Add<HDeclareGlobals>(array, flags);
     globals_.Rewind(0);
   }