chromeos: Fix accessibility text caret highlight in web contents

The text insertion caret in web contents can have a positive height but
zero width. Ensure the a11y highlight is still visible in this case.

This regressed in:
https://chromium-review.googlesource.com/c/chromium/src/+/1152373

due to the change to AccessibilityHighlightController::IsCaretVisible.

Bug: 882762
Test: added to ash_unittests
Change-Id: I2743cb234b49eb5c0d71ba5bf1d25e3869c2492f
Reviewed-on: https://chromium-review.googlesource.com/1241215Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Commit-Queue: James Cook <jamescook@chromium.org>
Cr-Commit-Position: refs/heads/master@{#593681}

ash/accessibility/accessibility_highlight_controller.cc

@@ -135,13 +135,19 @@ bool AccessibilityHighlightController::IsCursorVisible() {
 
 bool AccessibilityHighlightController::IsCaretVisible(
     const gfx::Rect& caret_bounds_in_screen) {
+  // Empty bounds are not visible. Don't use IsEmpty() because web contents
+  // carets can have positive height but zero width.
+  if (caret_bounds_in_screen.width() == 0 &&
+      caret_bounds_in_screen.height() == 0) {
+    return false;
+  }
+
   aura::Window* root_window = Shell::GetPrimaryRootWindow();
   aura::Window* active_window =
       ::wm::GetActivationClient(root_window)->GetActiveWindow();
   if (!active_window)
     active_window = root_window;
-  return !caret_bounds_in_screen.IsEmpty() &&
-         active_window->GetBoundsInScreen().Contains(caret_point_);
+  return active_window->GetBoundsInScreen().Contains(caret_point_);
 }
 
 void AccessibilityHighlightController::UpdateFocusAndCaretHighlights() {

ash/accessibility/accessibility_highlight_controller_unittest.cc

@@ -267,6 +267,34 @@ TEST_F(AccessibilityHighlightControllerTest, CaretRingDrawnOnlyWithinBounds) {
   EXPECT_FALSE(focus_ring_controller->caret_layer_for_testing());
 }
 
+// Tests that a zero-width text caret still results in a visible highlight.
+// https://crbug.com/882762
+TEST_F(AccessibilityHighlightControllerTest, ZeroWidthCaretRingVisible) {
+  AccessibilityHighlightController highlight_controller;
+  MockTextInputClient text_input_client;
+  highlight_controller.HighlightCaret(true);
+
+  // Simulate a zero-width text caret.
+  gfx::Rect zero_width(0, 16);
+  text_input_client.SetCaretBounds(zero_width);
+  highlight_controller.OnCaretBoundsChanged(&text_input_client);
+
+  // Caret ring is created.
+  EXPECT_TRUE(Shell::Get()
+                  ->accessibility_focus_ring_controller()
+                  ->caret_layer_for_testing());
+
+  // Simulate an empty text caret.
+  gfx::Rect empty;
+  text_input_client.SetCaretBounds(empty);
+  highlight_controller.OnCaretBoundsChanged(&text_input_client);
+
+  // Caret ring is gone.
+  EXPECT_FALSE(Shell::Get()
+                   ->accessibility_focus_ring_controller()
+                   ->caret_layer_for_testing());
+}
+
 // Tests setting the caret bounds explicitly via AccessibilityController, rather
 // than via the input method observer. This path is used in production in mash.
 TEST_F(AccessibilityHighlightControllerTest, SetCaretBounds) {