Variable to config: image.settings [d7]

I think that this issue should be postponed to D7. Right now the variables in D8:

 preview_image: core/modules/image/sample.png
 allow_insecure_derivatives: false
 suppress_itok_output: false

Itok integration was introduced in D7 see this for more information https://drupal.org/node/1934498
About insecure derivations was added in D7 7.20 see release note: https://drupal.org/drupal-7.20-release-notes
And the end the module in D6 isn't use any variable.

preview_image doesn't exist in d7 so no need to migrate it. These other two allow_insecure_derivatives and suppress_itok_output are straight forward boolean mappings so no complexity there I don't think.

Couldn't get the test suite working on my local so submitting for testbot.

tests now passing.

Committed to the drupal7 branch, fixed a small formatting issue on the way in.

Will need to be submitted again to Core since moving from sandbox.

Rerolled against 8.0.x, with a test of the d7_image_settings migration.

Slight cleanup of the test.

Blocked by #2495755: Create MigrateDrupal7TestBase.

Needs to be merged into the parent issue.

Needs to be re-rolled with fewer alterations to the {variable} dump.

We be re-rollin'. Testbot, don't be hatin'.

Re-rolled again. No interdiff due to merge conflict with Variable.php dump.

This looks straight-forward enough - but, despite what #7 says, in the D7 code base I see

  $sample_image = variable_get('image_style_preview_image', drupal_get_path('module', 'image') . '/sample.png');

I see absolutely no other reference to that variable in my D7 code base. I do see it included in #469798: Document variables without an UI. Should we migrate it?

If it exists in core, even for a single usage, I think we should migrate it.

Added image_style_preview_image.

Reroll.

Almost there.

1. +++ b/core/modules/image/src/Tests/Migrate/d7/MigrateImageSettingsTest.php
   @@ -0,0 +1,42 @@
   +    $this->installConfig(static::$modules);
   

   We might not actually need this line; if the test still passes without it, kill it. :)

2. +++ b/core/modules/image/src/Tests/Migrate/d7/MigrateImageSettingsTest.php
   @@ -0,0 +1,42 @@
   +    $this->loadDumps(['Variable.php']);
   

   This should be removed.

3. +++ b/core/modules/image/src/Tests/Migrate/d7/MigrateImageSettingsTest.php
   @@ -0,0 +1,42 @@
   +    $settings = \Drupal::config('image.settings')->get();
   

   $this->config()

4. +++ b/core/modules/image/src/Tests/Migrate/d7/MigrateImageSettingsTest.php
   @@ -0,0 +1,42 @@
   +    $this->assertTrue($settings['allow_insecure_derivatives']);
   +    $this->assertTrue($settings['suppress_itok_output']);
   +    $this->assertIdentical("core/modules/image/testsample.png",$settings['preview_image']);
   

   Let's use $config->get() here, for consistency.

Better?

Perfect.

Committed and pushed to 8.0.x. Thanks!