Eager autoload ActiveSupport::ExecutionContext

ExecutionContext was added as a regular autoload when it was introduced
in 6bad959. However, the class is not currently referenced anywhere on
the boot path. This means that the file will currently be required
during the first request/job/query (currently its loaded when the to_run
callback defined in active_support.reset_execution_context is executed).

To maximize CoW and ensure that the first request/job/query doesn't have
any extra latency, ExecutionContext should be eager autoloaded instead.

Author: skipkayhil

activesupport/lib/active_support.rb

@@ -41,7 +41,6 @@ module ActiveSupport
   autoload :CurrentAttributes
   autoload :Dependencies
   autoload :DescendantsTracker
-  autoload :ExecutionContext
   autoload :ExecutionWrapper
   autoload :Executor
   autoload :ErrorReporter
@@ -64,6 +63,7 @@ module ActiveSupport
     autoload :Configurable
     autoload :Deprecation
     autoload :Digest
+    autoload :ExecutionContext
     autoload :Gzip
     autoload :Inflector
     autoload :JSON