[turbofan] Optimize loads from the global object in JSTypeFeedbackSpecializer.

test/cctest/test-decls.cc

 // Copyright 2007-2008 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 905 matching lines @@
     context.Check(
         "'use strict';"
         "g({});0",
         EXPECT_RESULT, Number::New(CcTest::isolate(), 0));
     context.Check("f({})", EXPECT_RESULT, Number::New(CcTest::isolate(), 15));
     context.Check("h({})", EXPECT_RESULT, number_string);
   }
 }
 
 
+TEST(CrossScriptGlobal0) {

[Michael Starzinger, 2015/04/22 12:42:18]

nit: Do we need to add this test, since it's just apiece of the
CrossScriptGlobal below?

+  HandleScope handle_scope(CcTest::isolate());
+  {
+    SimpleContext context;
+
+    context.Check(
+        "var global = this;"
+        "global.x = 255;"
+        "x",
+        EXPECT_RESULT, Number::New(CcTest::isolate(), 255));
+    context.Check(
+        "'use strict';"
+        "let x = 1;"
+        "global.x",
+        EXPECT_RESULT, Number::New(CcTest::isolate(), 255));
+    context.Check("global.x = 15; x", EXPECT_RESULT,
+                  Number::New(CcTest::isolate(), 1));
+  }
+}
+
+
 TEST(CrossScriptGlobal) {
   HandleScope handle_scope(CcTest::isolate());
   {
     SimpleContext context;
 
     context.Check(
         "var global = this;"
         "global.x = 255;"
         "x",
         EXPECT_RESULT, Number::New(CcTest::isolate(), 255));
@@ skipping 305 matching lines @@
                   Undefined(CcTest::isolate()));
     for (int i = 0; i < 4; i++) {
       context.Check("f()", EXPECT_EXCEPTION);
     }
     context.Check("%OptimizeFunctionOnNextCall(f);", EXPECT_RESULT,
                   Undefined(CcTest::isolate()));
 
     context.Check("'use strict'; f(); let x = 2; x", EXPECT_EXCEPTION);
   }
 }