Stop exposing the download strategy from Formula

Library/Homebrew/formula.rb

@@ -48,7 +48,7 @@ class Formula
 
     @active_spec = determine_active_spec
     validate_attributes :url, :name, :version
-    @downloader = download_strategy.new(name, active_spec)
+    @downloader = active_spec.download_strategy.new(name, active_spec)
 
     # Combine DSL `option` and `def options`
     options.each do |opt, desc|
@@ -181,10 +181,6 @@ class Formula
     Pathname.new("#{HOMEBREW_PREFIX}/opt/#{name}")
   end
 
-  def download_strategy
-    active_spec.download_strategy
-  end
-
   def cached_download
     downloader.cached_location
   end

Library/Homebrew/test/test_formula.rb

@@ -175,7 +175,6 @@ class FormulaTests < Test::Unit::TestCase
     assert_equal 'http://example.com', f.homepage
     assert_version_equal '0.1', f.version
     assert_equal f.stable, f.active_spec
-    assert_equal CurlDownloadStrategy, f.download_strategy
     assert_instance_of CurlDownloadStrategy, f.downloader
 
     assert_instance_of SoftwareSpec, f.stable