harmony-scoping: Implement LoadIC handler for loads from global contexts.

src/contexts.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_CONTEXTS_H_
 #define V8_CONTEXTS_H_
 
 #include "src/heap/heap.h"
 #include "src/objects.h"
 
@@ skipping 211 matching lines @@
   // valid information about its location.
   // If it returns false, `result` is untouched.
   MUST_USE_RESULT
   static bool Lookup(Handle<GlobalContextTable> table, Handle<String> name,
                      LookupResult* result);
 
   MUST_USE_RESULT
   static Handle<GlobalContextTable> Extend(Handle<GlobalContextTable> table,
                                            Handle<Context> global_context);
 
+  static int GetContextOffset(int context_index) {
+    return kFirstContextOffset + context_index * kPointerSize;
+  }
+
  private:
   static const int kUsedSlot = 0;
+  static const int kFirstContextOffset =
+      FixedArray::kHeaderSize + (kUsedSlot + 1) * kPointerSize;
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(GlobalContextTable);
 };
 
 // JSFunctions are pairs (context, function code), sometimes also called
 // closures. A Context object is used to represent function contexts and
 // dynamically pushed 'with' contexts (or 'scopes' in ECMA-262 speak).
 //
 // At runtime, the contexts build a stack in parallel to the execution
 // stack, with the top-most context being the current context. All contexts
@@ skipping 361 matching lines @@
   static bool IsBootstrappingOrGlobalObject(Isolate* isolate, Object* object);
 #endif
 
   STATIC_ASSERT(kHeaderSize == Internals::kContextHeaderSize);
   STATIC_ASSERT(EMBEDDER_DATA_INDEX == Internals::kContextEmbedderDataIndex);
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_CONTEXTS_H_