Use text affinity to return correct accessible line boundaries.

content/renderer/accessibility/blink_ax_enum_conversion.cc

Index: content/renderer/accessibility/blink_ax_enum_conversion.cc
diff --git a/content/renderer/accessibility/blink_ax_enum_conversion.cc b/content/renderer/accessibility/blink_ax_enum_conversion.cc
index d438ca2aff1fee6922709c0c33a2988cde42dd24..76880152e0a81dfe364358fb941c0bb3a3ecffa7 100644
--- a/content/renderer/accessibility/blink_ax_enum_conversion.cc
+++ b/content/renderer/accessibility/blink_ax_enum_conversion.cc
@@ -551,4 +551,15 @@ ui::AXDescriptionFrom AXDescriptionFromFromBlink(
   return ui::AX_DESCRIPTION_FROM_NONE;
 }
 
+ui::AXTextAffinity AXTextAffinityFromBlink(blink::WebAXTextAffinity affinity) {
+  switch (affinity) {
+    case blink::WebAXTextAffinityUpstream:
+      return ui::AX_TEXT_AFFINITY_UPSTREAM;
+    case blink::WebAXTextAffinityDownstream:
+      return ui::AX_TEXT_AFFINITY_DOWNSTREAM;
+  }
+  NOTREACHED();
+  return ui::AX_TEXT_AFFINITY_DOWNSTREAM;
+}
+
 }  // namespace content.