[tracing] Add support to pre-load and merge ProcessMemoryDump(s).

base/trace_event/process_memory_dump_unittest.cc

+// Copyright 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/trace_event/process_memory_dump.h"
+
+#include "base/memory/scoped_ptr.h"
+#include "base/trace_event/trace_event_argument.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace base {
+namespace trace_event {
+
+TEST(ProcessMemoryDumpTest, TakeAllDumpsFrom) {
+  scoped_refptr<TracedValue> traced_value(new TracedValue());
+
+  scoped_ptr<ProcessMemoryDump> pmd1(new ProcessMemoryDump(nullptr));
+  pmd1->CreateAllocatorDump("pmd1/mad1");
+  pmd1->CreateAllocatorDump("pmd1/mad2");
+
+  scoped_ptr<ProcessMemoryDump> pmd2(new ProcessMemoryDump(nullptr));
+  pmd2->CreateAllocatorDump("pmd2/mad1");
+  pmd2->CreateAllocatorDump("pmd2/mad2");
+
+  pmd1->TakeAllDumpsFrom(pmd2.get());
+
+  // Make sure that pmd2 is empty but still usable after it has been emptied.
+  ASSERT_TRUE(pmd2->allocator_dumps().empty());
+  pmd2->CreateAllocatorDump("pmd2/this_mad_stays_with_pmd2");
+  ASSERT_EQ(1u, pmd2->allocator_dumps().size());
+  ASSERT_EQ(1u, pmd2->allocator_dumps().count("pmd2/this_mad_stays_with_pmd2"));
+
+  // Check that the AsValueInto doesn't cause a crash.
+  pmd2->AsValueInto(traced_value.get());
+
+  // Free the |pmd2| to check that the memory ownership of the two MAD(s) is

[petrcermak, 2015/05/21 08:17:38]

nit: s/is/has been/

P.S. I don't think you need the word "effectively" in any of the comments.

[Primiano Tucci (use gerrit), 2015/05/21 08:33:46]

Done
Was more a way to say "you can check that memory ownership has been really
transferred only if you free the objects and the contained objects are still
accessible"

+  // effectively moved to |pmd1|.
+  pmd2.reset();
+
+  // Now check that |pmd1| has been effectively merged.
+  ASSERT_EQ(4u, pmd1->allocator_dumps().size());
+  ASSERT_EQ(1u, pmd1->allocator_dumps().count("pmd1/mad1"));
+  ASSERT_EQ(1u, pmd1->allocator_dumps().count("pmd1/mad2"));
+  ASSERT_EQ(1u, pmd1->allocator_dumps().count("pmd2/mad1"));
+  ASSERT_EQ(1u, pmd1->allocator_dumps().count("pmd1/mad2"));
+
+  // Check that the AsValueInto doesn't cause a crash.
+  traced_value = new TracedValue();
+  pmd1->AsValueInto(traced_value.get());
+
+  pmd1.reset();
+}
+
+}  // namespace trace_event
+}  // namespace base