extensions: Abstract out install delay strategy

chrome/browser/extensions/install_gate.h

+// 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 CHROME_BROWSER_EXTENSIONS_INSTALL_GATE_H_
+#define CHROME_BROWSER_EXTENSIONS_INSTALL_GATE_H_
+
+namespace extensions {
+
+class Extension;
+
+// An interface that ExtensionService inquires for whether extension installs
+// should be delayed and whether to finish/abort delayed installs.
+class InstallGate {
+ public:
+  // Actions for a pending install.
+  enum Action {
+    INSTALL,  // Proceed to finish the install.
+    DELAY,    // Delay the install.
+    ABORT     // Abort the install.
+  };
+
+  virtual ~InstallGate() = default;
+
+  // Invoked by ExtensionService to check what to do with a pending install of
+  // the given extension. |extension| is an unpacked new extension to be
+  // installed. |install_immediately| is the flag associated with the install.
+  virtual Action ShouldDelay(const Extension* extension,
+                             bool install_immediately) = 0;
+};
+
+}  // namespace extensions
+
+#endif  // CHROME_BROWSER_EXTENSIONS_INSTALL_GATE_H_