Replace (slower) block.call with (faster) yield

Performance optimization: `yield` with an implicit `block` is faster than `block.call`.
See http://youtu.be/fGFM_UrSp70?t=10m35s and the following benchmark:

```ruby
require 'benchmark/ips'

def fast
 yield
end

def slow(&block)
 block.call
end

Benchmark.ips do |x|
 x.report('fast') { fast{} }
 x.report('slow') { slow{} }
end

# => fast    154095 i/100ms
# => slow     71454 i/100ms
# =>
# => fast  7511067.8 (±5.0%) i/s -   37445085 in   4.999660s
# => slow  1227576.9 (±6.8%) i/s -    6145044 in   5.028356s
```

1 files changed, 2 insertions, 2 deletions

diff --git a/railties/lib/rails/generators/actions/create_migration.rb b/railties/lib/rails/generators/actions/create_migration.rb
index 682092fdf2..cffdef6ec9 100644
--- a/railties/lib/rails/generators/actions/create_migration.rb
+++ b/railties/lib/rails/generators/actions/create_migration.rb
@@ -39,7 +39,7 @@ module Rails
 
         protected
 
-        def on_conflict_behavior(&block)
+        def on_conflict_behavior
           options = base.options.merge(config)
           if identical?
             say_status :identical, :blue, relative_existing_migration
@@ -48,7 +48,7 @@ module Rails
             say_status :create, :green
             unless pretend?
               ::FileUtils.rm_rf(existing_migration)
-              block.call
+              yield
             end
           elsif options[:skip]
             say_status :skip, :yellow