Use binread instead of setting file mode manually

Followup to b3102205.

actionpack/test/controller/api/data_streaming_test.rb

@@ -4,7 +4,7 @@
 
 module TestApiFileUtils
   def file_path() __FILE__ end
-  def file_data() @data ||= File.open(file_path, "rb") { |f| f.read } end
+  def file_data() @data ||= File.binread(file_path) end
 end
 
 class DataStreamingApiController < ActionController::API

actionpack/test/controller/send_file_test.rb

@@ -5,7 +5,7 @@
 module TestFileUtils
   def file_name() File.basename(__FILE__) end
   def file_path() __FILE__ end
-  def file_data() @data ||= File.open(file_path, "rb") { |f| f.read } end
+  def file_data() @data ||= File.binread(file_path) end
 end
 
 class SendFileController < ActionController::Base

activerecord/lib/active_record/fixture_set/render_context.rb

@@ -10,7 +10,7 @@ def get_binding
       end
 
       def binary(path)
-        %(!!binary "#{Base64.strict_encode64(File.read(path, mode: 'rb'))}")
+        %(!!binary "#{Base64.strict_encode64(File.binread(path))}")
       end
     end
   end

activerecord/test/cases/fixtures_test.rb

@@ -529,7 +529,7 @@ def test_subsubdir_file_with_arbitrary_name
   end
 
   def test_binary_in_fixtures
-    data = File.open(ASSETS_ROOT + "/flowers.jpg", "rb") { |f| f.read }
+    data = File.binread(ASSETS_ROOT + "/flowers.jpg")
     data.force_encoding("ASCII-8BIT")
     data.freeze
     assert_equal data, @flowers.data

railties/test/application/mailer_previews_test.rb

@@ -611,7 +611,7 @@ class Notifier < ActionMailer::Base
           default from: "from@example.com"
 
           def foo
-            attachments['pixel.png'] = File.read("#{app_path}/public/images/pixel.png", mode: 'rb')
+            attachments['pixel.png'] = File.binread("#{app_path}/public/images/pixel.png")
             mail to: "to@example.org"
           end
         end
@@ -648,7 +648,7 @@ class Notifier < ActionMailer::Base
           default from: "from@example.com"
 
           def foo
-            attachments['pixel.png'] = File.read("#{app_path}/public/images/pixel.png", mode: 'rb')
+            attachments['pixel.png'] = File.binread("#{app_path}/public/images/pixel.png")
             mail to: "to@example.org"
           end
         end
@@ -693,7 +693,7 @@ class Notifier < ActionMailer::Base
           default from: "from@example.com"
 
           def foo
-            attachments['pixel.png'] = File.read("#{app_path}/public/images/pixel.png", mode: 'rb')
+            attachments['pixel.png'] = File.binread("#{app_path}/public/images/pixel.png")
             mail to: "to@example.org"
           end
         end