Support persistent system profiles.

base/metrics/persistent_memory_allocator.cc

 // Copyright (c) 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "base/metrics/persistent_memory_allocator.h"
 
 #include <assert.h>
 #include <algorithm>
 
 #if defined(OS_WIN)
@@ skipping 144 matching lines @@
     : allocator_(allocator), last_record_(0), record_count_(0) {
   Reset(starting_after);
 }
 
 void PersistentMemoryAllocator::Iterator::Reset() {
   last_record_.store(kReferenceQueue, std::memory_order_relaxed);
   record_count_.store(0, std::memory_order_relaxed);
 }
 
 void PersistentMemoryAllocator::Iterator::Reset(Reference starting_after) {
+  if (starting_after == 0) {
+    Reset();
+    return;
+  }
+
   last_record_.store(starting_after, std::memory_order_relaxed);
   record_count_.store(0, std::memory_order_relaxed);
 
   // Ensure that the starting point is a valid, iterable block (meaning it can
   // be read and has a non-zero "next" pointer).
   const volatile BlockHeader* block =
       allocator_->GetBlock(starting_after, 0, 0, false, false);
   if (!block || block->next.load(std::memory_order_relaxed) == 0) {
     NOTREACHED();
     last_record_.store(kReferenceQueue, std::memory_order_release);
@@ skipping 988 matching lines @@
   if (!mem) {
     // This should never happen but be tolerant if it does as corruption from
     // the outside is something to guard against.
     NOTREACHED();
     return nullptr;
   }
   return mem + offset_;
 }
 
 }  // namespace base