Simplify and speed up address-to-page cache for conservative stack scanning.

Source/platform/heap/HeapTest.cpp

 /*
  * Copyright (C) 2013 Google Inc. 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
@@ skipping 1823 matching lines @@
 
 TEST(HeapTest, LargeObjects)
 {
     HeapStats initialHeapSize;
     clearOutOldGarbage(&initialHeapSize);
     IntWrapper::s_destructorCalls = 0;
     LargeObject::s_destructorCalls = 0;
     {
         int slack = 8; // LargeObject points to an IntWrapper that is also allocated.
         Persistent<LargeObject> object = LargeObject::create();
+        EXPECT_TRUE(ThreadState::current()->contains(object));
+        EXPECT_TRUE(ThreadState::current()->contains(reinterpret_cast<char*>(object.get()) + sizeof(LargeObject) - 1));
+#if ENABLE(GC_TRACING)
+        const GCInfo* info = ThreadState::current()->findGCInfo(reinterpret_cast<Address>(object.get()));
+        EXPECT_NE(reinterpret_cast<const GCInfo*>(0), info);
+        EXPECT_EQ(info, ThreadState::current()->findGCInfo(reinterpret_cast<Address>(object.get()) + sizeof(LargeObject) - 1));
+        EXPECT_NE(info, ThreadState::current()->findGCInfo(reinterpret_cast<Address>(object.get()) + sizeof(LargeObject)));
+        EXPECT_NE(info, ThreadState::current()->findGCInfo(reinterpret_cast<Address>(object.get()) - 1));
+#endif
         HeapStats afterAllocation;
         clearOutOldGarbage(&afterAllocation);
         {
             object->set(0, 'a');
             EXPECT_EQ('a', object->get(0));
             object->set(object->length() - 1, 'b');
             EXPECT_EQ('b', object->get(object->length() - 1));
             size_t expectedObjectSpace = sizeof(LargeObject) + sizeof(IntWrapper);
             size_t actualObjectSpace =
                 afterAllocation.totalObjectSpace() - initialHeapSize.totalObjectSpace();
@@ skipping 2020 matching lines @@
     {
         Persistent<MixinB> b = obj;
         Heap::collectGarbage(ThreadState::NoHeapPointersOnStack);
         EXPECT_EQ(0, IntWrapper::s_destructorCalls);
     }
     Heap::collectGarbage(ThreadState::NoHeapPointersOnStack);
     EXPECT_EQ(3, IntWrapper::s_destructorCalls);
 }
 
 } // WebCore namespace