diff --git a/modules/simpletest/files/css_test_files/css_input_with_import.css.optimized.css b/modules/simpletest/files/css_test_files/css_input_with_import.css.optimized.css
index 698d9aa..a05f939 100644
--- a/modules/simpletest/files/css_test_files/css_input_with_import.css.optimized.css
+++ b/modules/simpletest/files/css_test_files/css_input_with_import.css.optimized.css
@@ -1,4 +1,4 @@
-ul,select{font:1em/160% Verdana,sans-serif;color:#494949;}.ui-icon{background-image:url(images/icon.png);}
+ul,select{font:1em/160% Verdana,sans-serif;color:#494949;}.ui-icon{background-image:url(images/icon.png);}.data .double-quote{background-image:url("data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7");}.data .single-quote{background-image:url('data:image/jpeg;base64,/9j/4AAQSkZJRgABAQAAAQABAAD/2wBDACAWGBwYFCAcGhwkIiAmMFA0MCwsMGJGSjpQdGZ6eHJmcG6AkLicgIiuim5woNqirr7EztDOfJri8uDI8LjKzsb/2wBDASIkJDAqMF40NF7GhHCExsbGxsbGxsbGxsbGxsbGxsbGxsbGxsbGxsbGxsbGxsbGxsbGxsbGxsbGxsbGxsbGxsb/wAARCAABAAEDASIAAhEBAxEB/8QAFQABAQAAAAAAAAAAAAAAAAAAAAb/xAAUEAEAAAAAAAAAAAAAAAAAAAAA/8QAFAEBAAAAAAAAAAAAAAAAAAAAAP/EABQRAQAAAAAAAAAAAAAAAAAAAAD/2gAMAwEAAhEDEQA/AKAAH//Z');}.data .no-quote{background-image:url(data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAACEAAAAEAQAAAAAo/mtHAAAAIElEQVQIHWMRnWHwcRNLN8NZ7QYWwT8PlBlYsgqVBRsAankIMw5MtnoAAAAASUVORK5CYII=);}
 p,select{font:1em/160% Verdana,sans-serif;color:#494949;}
 body{margin:0;padding:0;background:#edf5fa;font:76%/170% Verdana,sans-serif;color:#494949;}.this .is .a .test{font:1em/100% Verdana,sans-serif;color:#494949;}.this
 .is
diff --git a/modules/simpletest/files/css_test_files/css_input_with_import.css.unoptimized.css b/modules/simpletest/files/css_test_files/css_input_with_import.css.unoptimized.css
index 19323c1..b8c7778 100644
--- a/modules/simpletest/files/css_test_files/css_input_with_import.css.unoptimized.css
+++ b/modules/simpletest/files/css_test_files/css_input_with_import.css.unoptimized.css
@@ -7,6 +7,21 @@ ul, select {
 }
 .ui-icon{background-image: url(images/icon.png);}
 
+/* Test data URI images with different quote styles. */
+.data .double-quote {
+  /* http://stackoverflow.com/a/13139830/11023 */
+  background-image: url("data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7");
+}
+
+.data .single-quote {
+  background-image: url('data:image/jpeg;base64,/9j/4AAQSkZJRgABAQAAAQABAAD/2wBDACAWGBwYFCAcGhwkIiAmMFA0MCwsMGJGSjpQdGZ6eHJmcG6AkLicgIiuim5woNqirr7EztDOfJri8uDI8LjKzsb/2wBDASIkJDAqMF40NF7GhHCExsbGxsbGxsbGxsbGxsbGxsbGxsbGxsbGxsbGxsbGxsbGxsbGxsbGxsbGxsbGxsbGxsb/wAARCAABAAEDASIAAhEBAxEB/8QAFQABAQAAAAAAAAAAAAAAAAAAAAb/xAAUEAEAAAAAAAAAAAAAAAAAAAAA/8QAFAEBAAAAAAAAAAAAAAAAAAAAAP/EABQRAQAAAAAAAAAAAAAAAAAAAAD/2gAMAwEAAhEDEQA/AKAAH//Z');
+}
+
+.data .no-quote {
+  background-image: url(data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAACEAAAAEAQAAAAAo/mtHAAAAIElEQVQIHWMRnWHwcRNLN8NZ7QYWwT8PlBlYsgqVBRsAankIMw5MtnoAAAAASUVORK5CYII=);
+}
+
+
 p, select {
   font: 1em/160% Verdana, sans-serif;
   color: #494949;
diff --git a/modules/simpletest/files/css_test_files/css_subfolder/css_input_with_import.css.optimized.css b/modules/simpletest/files/css_test_files/css_subfolder/css_input_with_import.css.optimized.css
index aba3b21..816039d 100644
--- a/modules/simpletest/files/css_test_files/css_subfolder/css_input_with_import.css.optimized.css
+++ b/modules/simpletest/files/css_test_files/css_subfolder/css_input_with_import.css.optimized.css
@@ -1,4 +1,4 @@
-ul,select{font:1em/160% Verdana,sans-serif;color:#494949;}.ui-icon{background-image:url(../images/icon.png);}
+ul,select{font:1em/160% Verdana,sans-serif;color:#494949;}.ui-icon{background-image:url(../images/icon.png);}.data .double-quote{background-image:url("data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7");}.data .single-quote{background-image:url('data:image/jpeg;base64,/9j/4AAQSkZJRgABAQAAAQABAAD/2wBDACAWGBwYFCAcGhwkIiAmMFA0MCwsMGJGSjpQdGZ6eHJmcG6AkLicgIiuim5woNqirr7EztDOfJri8uDI8LjKzsb/2wBDASIkJDAqMF40NF7GhHCExsbGxsbGxsbGxsbGxsbGxsbGxsbGxsbGxsbGxsbGxsbGxsbGxsbGxsbGxsbGxsbGxsb/wAARCAABAAEDASIAAhEBAxEB/8QAFQABAQAAAAAAAAAAAAAAAAAAAAb/xAAUEAEAAAAAAAAAAAAAAAAAAAAA/8QAFAEBAAAAAAAAAAAAAAAAAAAAAP/EABQRAQAAAAAAAAAAAAAAAAAAAAD/2gAMAwEAAhEDEQA/AKAAH//Z');}.data .no-quote{background-image:url(data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAACEAAAAEAQAAAAAo/mtHAAAAIElEQVQIHWMRnWHwcRNLN8NZ7QYWwT8PlBlYsgqVBRsAankIMw5MtnoAAAAASUVORK5CYII=);}
 p,select{font:1em/160% Verdana,sans-serif;color:#494949;}
 body{margin:0;padding:0;background:#edf5fa;font:76%/170% Verdana,sans-serif;color:#494949;}.this .is .a .test{font:1em/100% Verdana,sans-serif;color:#494949;}.this
 .is
diff --git a/modules/simpletest/files/css_test_files/css_subfolder/css_input_with_import.css.unoptimized.css b/modules/simpletest/files/css_test_files/css_subfolder/css_input_with_import.css.unoptimized.css
index 710d8f1..6d7151b 100644
--- a/modules/simpletest/files/css_test_files/css_subfolder/css_input_with_import.css.unoptimized.css
+++ b/modules/simpletest/files/css_test_files/css_subfolder/css_input_with_import.css.unoptimized.css
@@ -7,6 +7,21 @@ ul, select {
 }
 .ui-icon{background-image: url(../images/icon.png);}
 
+/* Test data URI images with different quote styles. */
+.data .double-quote {
+  /* http://stackoverflow.com/a/13139830/11023 */
+  background-image: url("data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7");
+}
+
+.data .single-quote {
+  background-image: url('data:image/jpeg;base64,/9j/4AAQSkZJRgABAQAAAQABAAD/2wBDACAWGBwYFCAcGhwkIiAmMFA0MCwsMGJGSjpQdGZ6eHJmcG6AkLicgIiuim5woNqirr7EztDOfJri8uDI8LjKzsb/2wBDASIkJDAqMF40NF7GhHCExsbGxsbGxsbGxsbGxsbGxsbGxsbGxsbGxsbGxsbGxsbGxsbGxsbGxsbGxsbGxsbGxsb/wAARCAABAAEDASIAAhEBAxEB/8QAFQABAQAAAAAAAAAAAAAAAAAAAAb/xAAUEAEAAAAAAAAAAAAAAAAAAAAA/8QAFAEBAAAAAAAAAAAAAAAAAAAAAP/EABQRAQAAAAAAAAAAAAAAAAAAAAD/2gAMAwEAAhEDEQA/AKAAH//Z');
+}
+
+.data .no-quote {
+  background-image: url(data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAACEAAAAEAQAAAAAo/mtHAAAAIElEQVQIHWMRnWHwcRNLN8NZ7QYWwT8PlBlYsgqVBRsAankIMw5MtnoAAAAASUVORK5CYII=);
+}
+
+
 p, select {
   font: 1em/160% Verdana, sans-serif;
   color: #494949;
diff --git a/modules/simpletest/files/css_test_files/import1.css b/modules/simpletest/files/css_test_files/import1.css
index 3d5842e..e53d6d5 100644
--- a/modules/simpletest/files/css_test_files/import1.css
+++ b/modules/simpletest/files/css_test_files/import1.css
@@ -3,4 +3,18 @@ ul, select {
   font: 1em/160% Verdana, sans-serif;
   color: #494949;
 }
-.ui-icon{background-image: url(images/icon.png);}
\ No newline at end of file
+.ui-icon{background-image: url(images/icon.png);}
+
+/* Test data URI images with different quote styles. */
+.data .double-quote {
+  /* http://stackoverflow.com/a/13139830/11023 */
+  background-image: url("data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7");
+}
+
+.data .single-quote {
+  background-image: url('data:image/jpeg;base64,/9j/4AAQSkZJRgABAQAAAQABAAD/2wBDACAWGBwYFCAcGhwkIiAmMFA0MCwsMGJGSjpQdGZ6eHJmcG6AkLicgIiuim5woNqirr7EztDOfJri8uDI8LjKzsb/2wBDASIkJDAqMF40NF7GhHCExsbGxsbGxsbGxsbGxsbGxsbGxsbGxsbGxsbGxsbGxsbGxsbGxsbGxsbGxsbGxsbGxsb/wAARCAABAAEDASIAAhEBAxEB/8QAFQABAQAAAAAAAAAAAAAAAAAAAAb/xAAUEAEAAAAAAAAAAAAAAAAAAAAA/8QAFAEBAAAAAAAAAAAAAAAAAAAAAP/EABQRAQAAAAAAAAAAAAAAAAAAAAD/2gAMAwEAAhEDEQA/AKAAH//Z');
+}
+
+.data .no-quote {
+  background-image: url(data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAACEAAAAEAQAAAAAo/mtHAAAAIElEQVQIHWMRnWHwcRNLN8NZ7QYWwT8PlBlYsgqVBRsAankIMw5MtnoAAAAASUVORK5CYII=);
+}
diff --git a/modules/simpletest/tests/common.test b/modules/simpletest/tests/common.test
index f6e03b0..903eac0 100644
--- a/modules/simpletest/tests/common.test
+++ b/modules/simpletest/tests/common.test
@@ -914,9 +914,10 @@ class CascadingStylesheetsUnitTest extends DrupalUnitTestCase {
    * Tests basic CSS loading with and without optimization via drupal_load_stylesheet().
    *
    * Known tests:
-   * - Retain white-space in selectors. (http://drupal.org/node/472820)
-   * - Proper URLs in imported files. (http://drupal.org/node/265719)
-   * - Retain pseudo-selectors. (http://drupal.org/node/460448)
+   * - Retain white-space in selectors. (https://drupal.org/node/472820)
+   * - Proper URLs in imported files. (https://drupal.org/node/265719)
+   * - Retain pseudo-selectors. (https://drupal.org/node/460448)
+   * - Don't adjust data URIs. (https://drupal.org/node/2142441)
    */
   function testLoadCssBasic() {
     // Array of files to test living in 'simpletest/files/css_test_files/'.