Apply the backtrace filter in the Json formatter.

When using the formatter callback functions the backtrace filter is
applied to the result objects before they are passed to the formatter
callback functions. When using events the formatters need to apply the
backtrace filter themselves.

features/docs/formatters/json_formatter.feature

@@ -286,7 +286,6 @@ Feature: JSON output formatter
 
       """
 
-  @spawn
   Scenario: DocString
     Given a file named "features/doc_string.feature" with:
       """
@@ -349,9 +348,8 @@ Feature: JSON output formatter
       ]
       """
 
-  @spawn
   Scenario: embedding screenshot
-    When I run `cucumber -b --format json features/embed.feature`
+    When I run `cucumber --format json features/embed.feature`
     Then it should pass with JSON:
     """
     [
@@ -630,9 +628,8 @@ Feature: JSON output formatter
 
     """
 
-  @spawn
   Scenario: embedding data directly
-    When I run `cucumber -b --format json -x features/embed_data_directly.feature`
+    When I run `cucumber --format json -x features/embed_data_directly.feature`
     Then it should pass with JSON:
     """
     [
@@ -733,7 +730,6 @@ Feature: JSON output formatter
     ]
 
     """
-  @spawn
   Scenario: handle output from hooks
      Given a file named "features/step_definitions/output_steps.rb" with:
       """

lib/cucumber/formatter/json.rb

@@ -1,5 +1,6 @@
 require 'multi_json'
 require 'base64'
+require 'cucumber/formatter/backtrace_filter'
 require 'cucumber/formatter/io'
 require 'cucumber/formatter/hook_query_visitor'
 
@@ -57,14 +58,14 @@ def on_before_test_step(event)
 
       def on_after_test_step(event)
         test_step = event.test_step
-        result = event.result
+        result = event.result.with_filtered_backtrace(Cucumber::Formatter::BacktraceFilter)
         return if internal_hook?(test_step)
         add_match_and_result(test_step, result)
         @any_step_failed = true if result.failed?
       end
 
       def on_after_test_case(event)
-        result = event.result
+        result = event.result.with_filtered_backtrace(Cucumber::Formatter::BacktraceFilter)
         add_failed_around_hook(result) if result.failed? && !@any_step_failed
       end