Focus affinity should be maintained if the requested text offset is equal to the caret offset

R=dmazzoni@chromium.org, aleventhal@chromium.org

Bug: 
Change-Id: I23f586ca63c037fb9a0adab24b090b694529d90c
Reviewed-on: https://chromium-review.googlesource.com/775520Reviewed-by: Dominic Mazzoni <dmazzoni@chromium.org>
Commit-Queue: Nektarios Paisios <nektar@chromium.org>
Cr-Commit-Position: refs/heads/master@{#517258}

content/browser/accessibility/browser_accessibility_com_win.cc

@@ -2261,14 +2261,15 @@ LONG BrowserAccessibilityComWin::FindBoundary(
     IA2TextBoundaryType ia2_boundary,
     LONG start_offset,
     ui::TextBoundaryDirection direction) {
-  // If the boundary is relative to the caret, use the selection
-  // affinity, otherwise default to downstream affinity.
-  ui::AXTextAffinity affinity =
-      start_offset == IA2_TEXT_OFFSET_CARET
-          ? Manager()->GetTreeData().sel_focus_affinity
-          : ui::AX_TEXT_AFFINITY_DOWNSTREAM;
-
   HandleSpecialTextOffset(&start_offset);
+  // If the |start_offset| is equal to the location of the caret, then use the
+  // focus affinity, otherwise default to downstream affinity.
+  ui::AXTextAffinity affinity = ui::AX_TEXT_AFFINITY_DOWNSTREAM;
+  int selection_start, selection_end;
+  GetSelectionOffsets(&selection_start, &selection_end);
+  if (selection_end >= 0 && start_offset == selection_end)
+    affinity = Manager()->GetTreeData().sel_focus_affinity;
+
   if (ia2_boundary == IA2_TEXT_BOUNDARY_WORD) {
     switch (direction) {
       case ui::FORWARDS_DIRECTION: {

ui/accessibility/platform/ax_platform_node_win.cc

@@ -3730,7 +3730,11 @@ void AXPlatformNodeWin::HandleSpecialTextOffset(LONG* offset) {
   if (*offset == IA2_TEXT_OFFSET_LENGTH) {
     *offset = static_cast<LONG>(GetText().length());
   } else if (*offset == IA2_TEXT_OFFSET_CARET) {
-    *offset = static_cast<LONG>(GetIntAttribute(AX_ATTR_TEXT_SEL_END));
+    int selection_start, selection_end;
+    GetSelectionOffsets(&selection_start, &selection_end);
+    if (selection_end < 0)
+      *offset = 0;
+    *offset = static_cast<LONG>(selection_end);
   }
 }