[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 1b8d4a1be58529d26673967fa43859fde6d0bb60..88bda0d4f2cbe39c473e6854023291cf7022d62f 100644
--- a/src/full-codegen/arm/full-codegen-arm.cc
+++ b/src/full-codegen/arm/full-codegen-arm.cc
@@ -803,6 +803,9 @@ void FullCodeGenerator::VisitVariableDeclaration(
       PrepareForBailoutForId(proxy->id(), BailoutState::NO_REGISTERS);
       break;
     }
+
+    case VariableLocation::MODULE:
+      UNREACHABLE();
   }
 }
 
@@ -862,6 +865,9 @@ void FullCodeGenerator::VisitFunctionDeclaration(
       PrepareForBailoutForId(proxy->id(), BailoutState::NO_REGISTERS);
       break;
     }
+
+    case VariableLocation::MODULE:
+      UNREACHABLE();
   }
 }
 
@@ -1350,7 +1356,11 @@ void FullCodeGenerator::EmitVariableLoad(VariableProxy* proxy,
       __ CallRuntime(function_id);
       __ bind(&done);
       context()->Plug(r0);
+      break;
     }
+
+    case VariableLocation::MODULE:
+      UNREACHABLE();
   }
 }