Add GenericSharedMemoryId and use w/ GpuMemoryBuffer

ui/gfx/generic_shared_memory_id.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 "ui/gfx/generic_shared_memory_id.h"
+
+#include "base/format_macros.h"
+#include "base/strings/stringprintf.h"
+
+namespace gfx {
+
+base::trace_event::MemoryAllocatorDumpGuid GetGenericSharedMemoryGUIDForTracing(
+    uint64_t tracing_process_id,
+    GenericSharedMemoryId generic_shared_memory_id) {
+  return base::trace_event::MemoryAllocatorDumpGuid(
+      base::StringPrintf("genericsharedmemory-x-process/%" PRIx64 "/%d",
+                         tracing_process_id, generic_shared_memory_id.id));
+}
+
+}  // namespace gfx