[Extensions Bindings] Add ExtensionBindingsSystem interface; hook it up

extensions/renderer/extension_bindings_system.h

Index: extensions/renderer/extension_bindings_system.h
diff --git a/extensions/renderer/extension_bindings_system.h b/extensions/renderer/extension_bindings_system.h
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+++ b/extensions/renderer/extension_bindings_system.h
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+// 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.
+
+#ifndef EXTENSIONS_RENDERER_EXTENSION_BINDINGS_SYSTEM_H_
+#define EXTENSIONS_RENDERER_EXTENSION_BINDINGS_SYSTEM_H_
+
+#include <string>
+
+namespace base {
+class DictionaryValue;
+class ListValue;
+}
+
+namespace extensions {
+class RequestSender;
+class ScriptContext;
+
+// The class responsible for creating extension bindings in different contexts,
+// as well as dispatching requests and handling responses, and dispatching
+// events to listeners.
+// This is designed to be used on a single thread, but should be safe to use on
+// threads other than the main thread (so that worker threads can have extension
+// bindings).
+class ExtensionBindingsSystem {
+ public:
+  virtual ~ExtensionBindingsSystem() {}
+
+  // Called when a new ScriptContext is created.
+  virtual void DidCreateScriptContext(ScriptContext* context) = 0;
+
+  // Called when a ScriptContext is about to be released.
+  virtual void WillReleaseScriptContext(ScriptContext* context) = 0;
+
+  // Updates the bindings for a given |context|. This happens at initialization,
+  // but also when e.g. an extension gets updated permissions.
+  virtual void UpdateBindingsForContext(ScriptContext* context) = 0;
+
+  // Dispatches an event with the given |name|, |event_args|, and
+  // |filtering_info| in the given |context|.
+  virtual void DispatchEventInContext(
+      const std::string& event_name,
+      const base::ListValue* event_args,
+      const base::DictionaryValue* filtering_info,
+      ScriptContext* context) = 0;
+
+  // Handles the response associated with the given |request_id|.
+  virtual void HandleResponse(int request_id,
+                              bool success,
+                              const base::ListValue& response,
+                              const std::string& error) = 0;
+
+  // Returns the associated RequestSender, if any.
+  // TODO(devlin): Factor this out.
+  virtual RequestSender* GetRequestSender() = 0;
+};
+
+}  // namespace extensions
+
+#endif  // EXTENSIONS_RENDERER_EXTENSION_BINDINGS_SYSTEM_H_