Add support to create memory allocator dump in base::DiscardableMemory

content/common/discardable_shared_memory_heap_unittest.cc

Index: content/common/discardable_shared_memory_heap_unittest.cc
diff --git a/content/common/discardable_shared_memory_heap_unittest.cc b/content/common/discardable_shared_memory_heap_unittest.cc
index c80d2c2e4bfd0f18a50e28437b37af24d358b5f5..a2befdc3329d7345b732393c6371c1549aeda348 100644
--- a/content/common/discardable_shared_memory_heap_unittest.cc
+++ b/content/common/discardable_shared_memory_heap_unittest.cc
@@ -302,5 +302,36 @@ TEST(DiscardableSharedMemoryHeapTest, DeletedCallback) {
   EXPECT_TRUE(deleted);
 }
 
+TEST(DiscardableSharedMemoryHeapTest, CreateMemoryAllocatorDumpTest) {
+  size_t block_size = base::GetPageSize();
+  DiscardableSharedMemoryHeap heap(block_size);
+  int next_discardable_shared_memory_id = 0;
+
+  scoped_ptr<base::DiscardableSharedMemory> memory(
+      new base::DiscardableSharedMemory);
+  ASSERT_TRUE(memory->CreateAndMap(block_size));
+  scoped_ptr<DiscardableSharedMemoryHeap::Span> span =
+      heap.Grow(memory.Pass(), block_size, next_discardable_shared_memory_id++,
+                base::Bind(NullTask));
+
+  // Unlock memory so it can be purged.
+  span->shared_memory()->Unlock(0, 0);

[reveman, 2015/08/22 14:21:16]

Keep in mind that there's no guarantee that memory is still present on all
platforms once you've called this. It might be purged when
CreateMemoryAllocatorDump is called below.

[ssid, 2015/08/22 14:50:19]

Ah, yes. I will move this after create dump, I did not think of that.

[ssid, 2015/08/24 14:52:10]

Done.

+
+  // Check if allocator dump is created when span exists.
+  scoped_ptr<base::trace_event::ProcessMemoryDump> pmd(
+      new base::trace_event::ProcessMemoryDump(nullptr));
+  EXPECT_TRUE(heap.CreateMemoryAllocatorDump(span.get(), "discardable/test1",
+                                             pmd.get()) != nullptr);
+
+  // Purge and release shared memory.
+  bool rv = span->shared_memory()->Purge(base::Time::Now());
+  EXPECT_TRUE(rv);
+  heap.ReleasePurgedMemory();
+
+  // Check that allocator dump is not created after memory is purged.
+  EXPECT_TRUE(heap.CreateMemoryAllocatorDump(span.get(), "discardable/test2",

[reveman, 2015/08/21 18:05:24]

hm, do we need a test for this? I'm worried that someone will exploit this to
figure out if some memory has been purged..

[ssid, 2015/08/21 19:02:30]

If you feel that then I will remove the purging part of the test. But otherwise
I have no other way to tell what I added really works.

[reveman, 2015/08/22 14:21:16]

You can keep the purging part but don't rely on some specific behavior except
having it produce a valid dump just like if the memory was still persistent.

[ssid, 2015/08/24 14:52:10]

Done.

+                                             pmd.get()) == nullptr);
+}
+
 }  // namespace
 }  // namespace content