Convert //extensions/browser from scoped_ptr to std::unique_ptr

BUG=554298
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Review URL: https://codereview.chromium.org/1909773002

Cr-Commit-Position: refs/heads/master@{#388687}
diff --git a/extensions/browser/mock_extension_system.h b/extensions/browser/mock_extension_system.h
index b926baad..c8748dfb 100644
--- a/extensions/browser/mock_extension_system.h
+++ b/extensions/browser/mock_extension_system.h
@@ -41,7 +41,7 @@
   AppSorting* app_sorting() override;
   const OneShotEvent& ready() const override;
   ContentVerifier* content_verifier() override;
-  scoped_ptr<ExtensionSet> GetDependentExtensions(
+  std::unique_ptr<ExtensionSet> GetDependentExtensions(
       const Extension* extension) override;
   void InstallUpdate(const std::string& extension_id,
                      const base::FilePath& temp_dir) override;