content: Fix problem with implementation of MergeIntoFreeList.

content/common/discardable_shared_memory_heap_unittest.cc

 // Copyright 2014 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 "content/common/discardable_shared_memory_heap.h"
 
 #include "base/memory/discardable_shared_memory.h"
 #include "base/process/process_metrics.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
@@ skipping 87 matching lines @@
 
   // All memory has been returned to the free list.
   scoped_ptr<DiscardableSharedMemoryHeap::Span> large_span =
       heap.SearchFreeList(kBlocks);
   ASSERT_TRUE(large_span);
 
   // Merge it into the free list again.
   heap.MergeIntoFreeList(large_span.Pass());
 }
 
+TEST_F(DiscardableSharedMemoryHeapTest, MergeSingleBlockSpan) {
+  size_t block_size = base::GetPageSize();
+  DiscardableSharedMemoryHeap heap(block_size);
+
+  const size_t kBlocks = 6;
+  size_t memory_size = block_size * kBlocks;
+
+  scoped_ptr<base::DiscardableSharedMemory> memory(
+      new base::DiscardableSharedMemory);
+  ASSERT_TRUE(memory->CreateAndMap(memory_size));
+  scoped_ptr<DiscardableSharedMemoryHeap::Span> new_span(
+      heap.Grow(memory.Pass(), memory_size));
+
+  // Split span into two.
+  scoped_ptr<DiscardableSharedMemoryHeap::Span> leftover =
+      heap.Split(new_span.get(), 5);
+  ASSERT_TRUE(leftover);
+
+  // Merge |new_span| into free list.
+  heap.MergeIntoFreeList(new_span.Pass());
+
+  // Merge |leftover| into free list.
+  heap.MergeIntoFreeList(leftover.Pass());
+}
+
 TEST_F(DiscardableSharedMemoryHeapTest, Grow) {
   size_t block_size = base::GetPageSize();
   DiscardableSharedMemoryHeap heap(block_size);
 
   scoped_ptr<base::DiscardableSharedMemory> memory1(
       new base::DiscardableSharedMemory);
   ASSERT_TRUE(memory1->CreateAndMap(block_size));
   heap.MergeIntoFreeList(heap.Grow(memory1.Pass(), block_size).Pass());
 
   // Remove a span from free list.
@@ skipping 35 matching lines @@
   bool rv = span->shared_memory()->Purge(base::Time::Now());
   EXPECT_TRUE(rv);
   heap.ReleaseFreeMemory();
 
   // Shared memory backing for |span| should be gone.
   EXPECT_FALSE(span->shared_memory());
 }
 
 }  // namespace
 }  // namespace content