Resubmit change 6302 after fixing the compiler warning on older GCC compiler versions:

vm/pages.cc

Index: vm/pages.cc
===================================================================
--- vm/pages.cc	(revision 6329)
+++ vm/pages.cc	(working copy)
@@ -49,6 +49,21 @@
 }
 
 
+RawObject* HeapPage::FindObject(FindObjectVisitor* visitor) const {
+  uword obj_addr = first_object_start();
+  uword end_addr = top();
+  while (obj_addr < end_addr) {
+    RawObject* raw_obj = RawObject::FromAddr(obj_addr);
+    if (raw_obj->FindObject(visitor)) {
+      return raw_obj;  // Found object, return it.
+    }
+    obj_addr += raw_obj->Size();
+  }
+  ASSERT(obj_addr == end_addr);
+  return Object::null();
+}
+
+
 PageSpace::PageSpace(Heap* heap, intptr_t max_capacity, bool is_executable)
     : freelist_(),
       heap_(heap),
@@ -206,6 +221,29 @@
 }
 
 
+RawObject* PageSpace::FindObject(FindObjectVisitor* visitor) const {
+  ASSERT(Isolate::Current()->no_gc_scope_depth() != 0);
+  HeapPage* page = pages_;
+  while (page != NULL) {
+    RawObject* obj = page->FindObject(visitor);
+    if (obj != Object::null()) {
+      return obj;
+    }
+    page = page->next();
+  }
+
+  page = large_pages_;
+  while (page != NULL) {
+    RawObject* obj = page->FindObject(visitor);
+    if (obj != Object::null()) {
+      return obj;
+    }
+    page = page->next();
+  }
+  return Object::null();
+}
+
+
 void PageSpace::MarkSweep(bool invoke_api_callbacks) {
   // MarkSweep is not reentrant. Make sure that is the case.
   ASSERT(!sweeping_);