Introduce mojo interface for collecting StackSamplingProfiler data

components/metrics/public/cpp/BUILD.gn

+# Copyright 2016 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.
+
+import("//mojo/public/tools/bindings/mojom.gni")
+
+source_set("unit_tests") {
+  testonly = true
+  sources = [
+    "call_stack_profile_struct_traits_unittest.cc",
+  ]
+
+  # iOS is not supported by the profiler and the ios-simulator bot chokes on
+  # this test.
+  if (is_ios) {
+    sources -= [ "call_stack_profile_struct_traits_unittest.cc" ]
+  }
+
+  deps = [
+    "//base",
+    "//components/metrics/public/interfaces:mojo_test_bindings",
+    "//mojo/public/cpp/bindings",
+    "//testing/gtest",
+  ]
+}