[modules] Introduce new VariableLocation for module imports/exports.

src/full-codegen/arm/full-codegen-arm.cc

Index: src/full-codegen/arm/full-codegen-arm.cc
diff --git a/src/full-codegen/arm/full-codegen-arm.cc b/src/full-codegen/arm/full-codegen-arm.cc
index 68ae0dcebf58fc998459ee6d0c1578430deae242..66816fd2f701556868ac22070732fb84f79d3ff2 100644
--- a/src/full-codegen/arm/full-codegen-arm.cc
+++ b/src/full-codegen/arm/full-codegen-arm.cc
@@ -807,6 +807,9 @@ void FullCodeGenerator::VisitVariableDeclaration(
       PrepareForBailoutForId(proxy->id(), BailoutState::NO_REGISTERS);
       break;
     }
+
+    case VariableLocation::MODULE:
+      UNREACHABLE();
   }
 }
 
@@ -866,6 +869,9 @@ void FullCodeGenerator::VisitFunctionDeclaration(
       PrepareForBailoutForId(proxy->id(), BailoutState::NO_REGISTERS);
       break;
     }
+
+    case VariableLocation::MODULE:
+      UNREACHABLE();
   }
 }
 
@@ -1356,7 +1362,11 @@ void FullCodeGenerator::EmitVariableLoad(VariableProxy* proxy,
       __ CallRuntime(function_id);
       __ bind(&done);
       context()->Plug(r0);
+      break;
     }
+
+    case VariableLocation::MODULE:
+      UNREACHABLE();
   }
 }