Add figcaption case at 'computeAccessibilityIsIgnored()'

to keep figcation infomation on accessibility tree.

BUG=None

Review URL: https://codereview.chromium.org/553033002

git-svn-id: svn://svn.chromium.org/blink/trunk@181681 bbb929c8-8fbe-4397-9dbb-9b2b20218538

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

@@ -677,6 +677,9 @@ bool AXRenderObject::computeAccessibilityIsIgnored() const
     if (roleValue() == DialogRole)
         return false;
 
+    if (roleValue() == FigcaptionRole)
+        return false;
+
     if (roleValue() == FigureRole)
         return false;