Don't require expectations file for DumpAccessibility tests.

content/content_tests.gypi

Index: content/content_tests.gypi
diff --git a/content/content_tests.gypi b/content/content_tests.gypi
index 0c14ccfeb9d301e7681a92f87617e73e8612f68a..df67e0b3a664830693d11f9cfe8e471db8e627df 100644
--- a/content/content_tests.gypi
+++ b/content/content_tests.gypi
@@ -1508,11 +1508,6 @@
                 '../base/allocator/allocator.gyp:allocator',
               ],
             }],
-            ['OS=="linux"', {
-              'sources!': [
-                'browser/accessibility/dump_accessibility_tree_browsertest.cc',
-              ],
-            }],
             ['OS=="android"', {
               'sources': [ '<@(content_browsertests_android_sources)' ],
               'sources!': [