Inherit Presentation role only when elements without a explicit role defined.

LayoutTests/accessibility/listitem-presentation-inherited-expected.txt

Index: LayoutTests/accessibility/listitem-presentation-inherited-expected.txt
diff --git a/LayoutTests/accessibility/listitem-presentation-inherited-expected.txt b/LayoutTests/accessibility/listitem-presentation-inherited-expected.txt
new file mode 100644
index 0000000000000000000000000000000000000000..d7cbbdbb81205efb57180fec489ba9133c812827
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+++ b/LayoutTests/accessibility/listitem-presentation-inherited-expected.txt
@@ -0,0 +1,41 @@
+Item 1
+Item 2
+Item 3
+Plain Text 1
+Plain Text 2
+Plain Text 3
+End of test
+
+This tests that the presentation role is inherited.
+
+On success, you will see a series of "PASS" messages, followed by "TEST COMPLETE".
+
+
+AXRole: AXWebArea AXValue: 
+    AXRole: AXListItem AXValue: 
+        AXRole: AXListMarker AXValue: •
+        AXRole: AXStaticText AXValue: Item 1
+            AXRole: AXInlineTextBox AXValue: Item 1
+    AXRole: AXListItem AXValue: 
+        AXRole: AXListMarker AXValue: •
+        AXRole: AXStaticText AXValue: Item 2
+            AXRole: AXInlineTextBox AXValue: Item 2
+    AXRole: AXListItem AXValue: 
+        AXRole: AXListMarker AXValue: •
+        AXRole: AXStaticText AXValue: Item 3
+            AXRole: AXInlineTextBox AXValue: Item 3
+    AXRole: AXListMarker AXValue: •
+    AXRole: AXStaticText AXValue: Plain Text 1
+        AXRole: AXInlineTextBox AXValue: Plain Text 1
+    AXRole: AXListMarker AXValue: •
+    AXRole: AXStaticText AXValue: Plain Text 2
+        AXRole: AXInlineTextBox AXValue: Plain Text 2
+    AXRole: AXListMarker AXValue: •
+    AXRole: AXStaticText AXValue: Plain Text 3
+        AXRole: AXInlineTextBox AXValue: Plain Text 3
+    AXRole: AXParagraph AXValue: 
+        AXRole: AXStaticText AXValue: End of test
+PASS successfullyParsed is true
+
+TEST COMPLETE
+