Add GenericSharedMemoryId and use w/ GpuMemoryBuffer

base/memory/generic_shared_memory_id.h

Index: base/memory/generic_shared_memory_id.h
diff --git a/base/memory/generic_shared_memory_id.h b/base/memory/generic_shared_memory_id.h
new file mode 100644
index 0000000000000000000000000000000000000000..a55c71098fdbfb696be930b50d7fd9ff496776be
--- /dev/null
+++ b/base/memory/generic_shared_memory_id.h
@@ -0,0 +1,31 @@
+// 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.
+
+#ifndef BASE_MEMORY_GENERIC_SHARED_MEMORY_ID_H_
+#define BASE_MEMORY_GENERIC_SHARED_MEMORY_ID_H_
+
+#include "base/base_export.h"
+#include "base/trace_event/memory_allocator_dump.h"
+
+namespace base {
+
+namespace memory {
+
+// Defines an ID type which is used accross all types of shared memory
+// allocations. This includes other types (IOSurfaces, SharedBitmaps), not
+// just base::SharedMemory.
+using GenericSharedMemoryId = int;

[Tom Sepez, 2015/08/06 00:11:08]

do we want to use a specific-sized unsigned type like uint32_t?

[reveman, 2015/08/06 04:25:06]

+1

[ericrk, 2015/08/06 18:28:08]

The underlying code uses base::StaticAtomicSequenceNumber, which returns an int
(matching existing GpuMemoryBufferId, which was an int itself)... I could switch
to uint32_t, but would need to tweak the generation code. WDYT?

[reveman, 2015/08/06 19:19:36]

I think it's fine to keep this as 'int' then unless we change
base::StaticAtomicSequenceNumber.

+
+// Generates GUID which can be used to trace shared memory using its
+// GenericSharedMemoryId.
+BASE_EXPORT base::trace_event::MemoryAllocatorDumpGuid
+GetGenericSharedMemoryGUIDForTracing(
+    uint64_t tracing_process_id,
+    GenericSharedMemoryId generic_shared_memory_id);
+
+}  // namespace memory
+
+}  // namespace base
+
+#endif  // BASE_MEMORY_GENERIC_SHARED_MEMORY_ID_H_