hr tag should return SplitterRole.

Remove redundant role HorizontalRuleRole. HR tag should return SplitterRole.

This CL depends on https://codereview.chromium.org/709523002/

BUG=384723

Review URL: https://codereview.chromium.org/703033006

git-svn-id: svn://svn.chromium.org/blink/trunk@185053 bbb929c8-8fbe-4397-9dbb-9b2b20218538

third_party/WebKit/Source/core/accessibility/AXObject.h

@@ -95,7 +95,6 @@ enum AccessibilityRole {
     GrowAreaRole,
     HeadingRole,
     HelpTagRole,
-    HorizontalRuleRole,
     IframeRole,
     IgnoredRole,
     ImageMapLinkRole,

third_party/WebKit/Source/core/accessibility/AXRenderObject.cpp

@@ -374,7 +374,7 @@ AccessibilityRole AXRenderObject::determineAccessibilityRole()
         return IgnoredRole;
 
     if (m_renderer->isHR())
-        return HorizontalRuleRole;
+        return SplitterRole;
 
     if (isHTMLOutputElement(node))
         return StatusRole;

third_party/WebKit/public/web/WebAXEnums.h

@@ -114,7 +114,6 @@ enum WebAXRole {
     WebAXRoleGrowArea,
     WebAXRoleHeading,
     WebAXRoleHelpTag,
-    WebAXRoleHorizontalRule,
     WebAXRoleIframe,
     WebAXRoleIgnored,
     WebAXRoleImageMapLink,