Remove dependency on actionpack in ActionView::AssetPaths

Since Action View should not depend on actionpack, it's best to delegate
invalid_asset_host! to controller and just rely on such simple contract
instead of raising ActionController::RoutingError directly.

actionpack/lib/action_controller.rb

@@ -12,6 +12,7 @@ module ActionController
   autoload :Middleware
 
   autoload_under "metal" do
+    autoload :AssetPaths
     autoload :Compatibility
     autoload :ConditionalGet
     autoload :Cookies

actionpack/lib/action_controller/base.rb

@@ -183,8 +183,8 @@ def self.without_modules(*modules)
     MODULES = [
       AbstractController::Layouts,
       AbstractController::Translation,
-      AbstractController::AssetPaths,
 
+      AssetPaths,
       Helpers,
       HideActions,
       UrlFor,

actionpack/lib/action_controller/metal/asset_paths.rb

@@ -0,0 +1,15 @@
+require 'action_controller/metal/exceptions'
+
+module ActionController
+  module AssetPaths
+    extend ActiveSupport::Concern
+
+    included do
+      include AbstractController::AssetPaths
+    end
+
+    def invalid_asset_host!(help_message)
+      raise ActionController::RoutingError, "This asset host cannot be computed without a request in scope. #{help_message}"
+    end
+  end
+end

actionpack/lib/action_view/asset_paths.rb

@@ -1,13 +1,15 @@
 require 'zlib'
 require 'active_support/core_ext/file'
-require 'action_controller/metal/exceptions'
+require 'active_support/core_ext/module/delegation'
 
 module ActionView
   class AssetPaths #:nodoc:
     URI_REGEXP = %r{^[-a-z]+://|^(?:cid|data):|^//}
 
     attr_reader :config, :controller
 
+    delegate :invalid_asset_host!, :to => :controller, :prefix => false
+
     def initialize(config, controller = nil)
       @config = config
       @controller = controller
@@ -97,10 +99,6 @@ def default_protocol
       @config.default_asset_host_protocol || (has_request? ? :request : :relative)
     end
 
-    def invalid_asset_host!(help_message)
-      raise ActionController::RoutingError, "This asset host cannot be computed without a request in scope. #{help_message}"
-    end
-
     # Pick an asset host for this source. Returns +nil+ if no host is set,
     # the host if no wildcard is set, the host interpolated with the
     # numbers 0-3 if it contains <tt>%d</tt> (the number is the source hash mod 4),