Fix compilation with clang

src/heap-snapshot-generator.cc

 // Copyright 2013 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 184 matching lines @@
   static const int kExpectedHeapEntrySize = 24;
 };
 
 template <> struct SnapshotSizeConstants<8> {
   static const int kExpectedHeapGraphEdgeSize = 24;
   static const int kExpectedHeapEntrySize = 32;
 };
 
 }  // namespace
 
+
 HeapSnapshot::HeapSnapshot(HeapProfiler* profiler,
                            const char* title,
                            unsigned uid)
     : profiler_(profiler),
       title_(title),
       uid_(uid),
       root_index_(HeapEntry::kNoEntry),
       gc_roots_index_(HeapEntry::kNoEntry),
       natives_root_index_(HeapEntry::kNoEntry),
       max_snapshot_js_object_id_(0) {
   STATIC_CHECK(
       sizeof(HeapGraphEdge) ==
       SnapshotSizeConstants<kPointerSize>::kExpectedHeapGraphEdgeSize);
   STATIC_CHECK(
       sizeof(HeapEntry) ==
       SnapshotSizeConstants<kPointerSize>::kExpectedHeapEntrySize);
+  USE(SnapshotSizeConstants<4>::kExpectedHeapGraphEdgeSize);
+  USE(SnapshotSizeConstants<4>::kExpectedHeapEntrySize);
+  USE(SnapshotSizeConstants<8>::kExpectedHeapGraphEdgeSize);
+  USE(SnapshotSizeConstants<8>::kExpectedHeapEntrySize);
   for (int i = 0; i < VisitorSynchronization::kNumberOfSyncTags; ++i) {
     gc_subroot_indexes_[i] = HeapEntry::kNoEntry;
   }
 }
 
 
 void HeapSnapshot::Delete() {
   profiler_->RemoveSnapshot(this);
   delete this;
 }
@@ skipping 2723 matching lines @@
   writer_->AddString("\"<dummy>\"");
   for (int i = 1; i < sorted_strings.length(); ++i) {
     writer_->AddCharacter(',');
     SerializeString(sorted_strings[i]);
     if (writer_->aborted()) return;
   }
 }
 
 
 } }  // namespace v8::internal