Create MetricsPrivateDelegate for metricsPrivate behavior

extensions/shell/browser/api/metrics_private/shell_metrics_private_delegate.h

+// Copyright 2016 The Chromium Authors. All rights reserved.

[Devlin, 2016/09/26 16:27:13]

When is this used?

[Rahul Chaturvedi, 2016/09/26 18:22:59]

https://codereview.chromium.org/2331343012/diff/20001/extensions/shell/browse...

[Devlin, 2016/09/26 18:26:31]

Right, but the object offers no value there.  I don't see the point in adding a
shell implementation if it provides no functionality.  It would be easier and
far less code to just do:
is_crash_reporting_enabled = delegate && delegate->IsCrashReportingEnabled();

We have a lot of unnecessary shell delegate implementations already, and it
makes finding out where the behavior is fundamentally different very difficult. 
If we only provide an implementation when it's actually usable, it's far simpler
to trace down potential code paths.

[michaelpg, 2016/09/27 00:07:44]

I like that idea, in general. We wouldn't have to change
shell_extensions_api_client.* either. rkc^H^H^Hsteel, are you OK with that?

There's a tangential discussion in CrOS about how to structure
services/dependencies -- main question is how to handle ownership, existence,
and fetching of services from different processes. See
https://docs.google.com/a/google.com/document/d/16pmp3Vpe1fIzdjakwyEw2Fn2HjX5...

[michaelpg, 2016/09/27 00:09:30]

(although I'll note, we do need to add that functionality later.)

[Rahul Chaturvedi, 2016/09/27 18:41:57]

I like the idea of adding functionality when needed, so sgtm.

+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef EXTENSIONS_SHELL_BROWSER_API_METRICS_PRIVATE_SHELL_METRICS_PRIVATE_DELEGATE_H_
+#define EXTENSIONS_SHELL_BROWSER_API_METRICS_PRIVATE_SHELL_METRICS_PRIVATE_DELEGATE_H_
+
+#include "base/macros.h"
+#include "extensions/browser/api/metrics_private/metrics_private_delegate.h"
+
+namespace extensions {
+
+class ShellMetricsPrivateDelegate : public MetricsPrivateDelegate {
+ public:
+  ShellMetricsPrivateDelegate() {}
+  ~ShellMetricsPrivateDelegate() override {}
+
+  bool IsCrashReportingEnabled() override;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(ShellMetricsPrivateDelegate);
+};
+
+}  // namespace extensions
+
+#endif  // EXTENSIONS_SHELL_BROWSER_API_METRICS_PRIVATE_SHELL_METRICS_PRIVATE_DELEGATE_H_