memory-infra: Introduce mojo interfaces and service stubs

services/memory_infra/public/interfaces/memory_infra.mojom

+// Copyright 2017 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.
+
+module memory_infra.mojom;
+
+enum DumpType {
+  PERIODIC_INTERVAL,
+  EXPLICITLY_TRIGGERED,
+  PEAK_MEMORY_USAGE
+};
+
+enum LevelOfDetail {
+  BACKGROUND,
+  LIGHT,
+  DETAILED
+};
+
+struct RequestArgs {
+  uint64 dump_guid;
+  DumpType dump_type;
+  LevelOfDetail level_of_detail;
+};
+
+// Memory Infra clients implement this interface. There should be at most one
+// client per process. 

[Primiano Tucci (use gerrit), 2017/01/16 15:11:04]

maybe expand a bit more saying. When successful, the dump is appended in the
process-local trace buffer of the target process and only a ACK is returned.

[chiniforooshan1, 2017/01/16 18:14:48]

Done.

+interface Client {

[Primiano Tucci (use gerrit), 2017/01/16 15:11:04]

naming bike-shedding, yay: client may be a bit generic, because "memory infra
client" might also mean "something external which is totally unaware of the
internal operations of memory-infra and just wants to see an API to request a
dump". for instance, this is what devtools does today, in that sense they are a
"memory-infra client" although that "client" is semantically different from this
notion of client :)
could this be ProcessLocalDumpManager or something that emphasizes that this is
really bound to the notion of the current process?

[chiniforooshan1, 2017/01/16 18:14:48]

Done.

+  RequestProcessMemoryDump(RequestArgs args) =>
+      (uint64 dump_guid, bool success);
+};
+
+// Memory Infra service implements this interface. Clients register themselves
+// using the RegisterClient method and suggest a global memory dump using the
+// RequestGlobalMemoryDump method.
+interface Coordinator {
+  RegisterClient(Client client);
+  RequestGlobalMemoryDump(RequestArgs args) => (uint64 dump_guid, bool success);
+};