Modify AX AriaGrabbed test and enable it.

content/browser/accessibility/dump_accessibility_tree_browsertest.cc

Index: content/browser/accessibility/dump_accessibility_tree_browsertest.cc
diff --git a/content/browser/accessibility/dump_accessibility_tree_browsertest.cc b/content/browser/accessibility/dump_accessibility_tree_browsertest.cc
index 99896254f776b5ef3cfc8174867f1c4ba22629d1..ca5ab7bba40091769338501f0991eb99ef4fe9a7 100644
--- a/content/browser/accessibility/dump_accessibility_tree_browsertest.cc
+++ b/content/browser/accessibility/dump_accessibility_tree_browsertest.cc
@@ -264,8 +264,7 @@ IN_PROC_BROWSER_TEST_F(DumpAccessibilityTreeTest, AccessibilityAriaForm) {
   RunAriaTest(FILE_PATH_LITERAL("aria-form.html"));
 }
 
-IN_PROC_BROWSER_TEST_F(DumpAccessibilityTreeTest,
-                       DISABLED_AccessibilityAriaGrabbed) {
+IN_PROC_BROWSER_TEST_F(DumpAccessibilityTreeTest, AccessibilityAriaGrabbed) {
   RunAriaTest(FILE_PATH_LITERAL("aria-grabbed.html"));
 }