Reland "[a11y] Add scrolling action to PP_PDF_SET_SELECTION"

This is a reland of 9b07e5e0 with
a fix of a failure on Linux MSan Test builder.

Added an initial value for |action_data.target_rect| to
AccessibilityTest.TestSelectionActionHandling.

Original change's description:
> [a11y] Add scrolling action to PP_PDF_SET_SELECTION
>
> This CL adds scrolling when PDFiumEngine::HandleAccessibilityAction
> is called with PP_PDF_SET_SELECTION and the selection is not
> visible since Blink triggers also scrolling with setting selection.
> So, this change makes PDF document scroll the page when a selection
> is set.
>
> AX-Relnotes: When SetSelection action is handled on pdf, it also
> triggers scrolling if the selection is not in the visible area.
> For instance, atk_text_set_caret_offset() on pdf scrolls the page
> if the text is not in the view port.
>
> Bug: 993456
> Change-Id: I8323eff293b3216e2b862f8df3e896380b1c9945
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2573975
> Reviewed-by: Dominic Mazzoni <dmazzoni@chromium.org>
> Reviewed-by: K. Moon <kmoon@chromium.org>
> Reviewed-by: Martin Robinson <mrobinson@igalia.com>
> Commit-Queue: Julie Kim <jkim@igalia.com>
> Cr-Commit-Position: refs/heads/master@{#835994}

Bug: 993456
Change-Id: Ie7c683d062c50d4eade2b5fb4990bc6ca2be12ba
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2586644Reviewed-by: K. Moon <kmoon@chromium.org>
Commit-Queue: Julie Kim <jkim@igalia.com>
Cr-Commit-Position: refs/heads/master@{#836377}

components/pdf/renderer/pdf_ax_action_target.cc

@@ -144,6 +144,11 @@ bool PdfAXActionTarget::SetSelection(const ui::AXActionTarget* anchor_object,
     return false;
   }
   pdf_action_data.action = PP_PdfAccessibilityAction::PP_PDF_SET_SELECTION;
+  pdf_action_data.target_rect = {
+      {target_plugin_node_.data().relative_bounds.bounds.x(),
+       target_plugin_node_.data().relative_bounds.bounds.y()},
+      {target_plugin_node_.data().relative_bounds.bounds.width(),
+       target_plugin_node_.data().relative_bounds.bounds.height()}};
   pdf_accessibility_tree_source_->HandleAction(pdf_action_data);
   return true;
 }

pdf/pdfium/accessibility_unittest.cc

@@ -651,6 +651,7 @@ TEST_F(AccessibilityTest, TestSelectionActionHandling) {
     action_data.selection_start_index.char_index = sel_action.start_char_index;
     action_data.selection_end_index.page_index = sel_action.end_page_index;
     action_data.selection_end_index.char_index = sel_action.end_char_index;
+    action_data.target_rect = {{0, 0}, {0, 0}};
 
     engine->HandleAccessibilityAction(action_data);
     Selection actual_selection;
@@ -669,4 +670,64 @@ TEST_F(AccessibilityTest, TestSelectionActionHandling) {
   }
 }
 
+// Tests if PP_PDF_SET_SELECTION updates scroll offsets if the selection is not
+// in the current visible rect.
+TEST_F(AccessibilityTest, TestSetSelectionAndScroll) {
+  struct Selection {
+    uint32_t start_page_index;
+    uint32_t start_char_index;
+    uint32_t end_page_index;
+    uint32_t end_char_index;
+  };
+
+  struct TestCase {
+    Selection action;
+    Selection expected_result;
+    gfx::Vector2d scroll_offset;
+  };
+
+  static constexpr TestCase kTestCases[] = {
+      {{0, 15, 0, 15}, {0, 15, 0, 15}, {0, 0}},
+      {{1, 15, 1, 15}, {1, 15, 1, 15}, {28, 517}},
+  };
+
+  ScrollEnabledTestClient client;
+  std::unique_ptr<PDFiumEngine> engine =
+      InitializeEngine(&client, FILE_PATH_LITERAL("hello_world2.pdf"));
+  ASSERT_TRUE(engine);
+  engine->PluginSizeUpdated({400, 400});
+
+  int index = 0;
+  for (const auto& test_case : kTestCases) {
+    PP_PdfAccessibilityActionData action_data;
+    action_data.action = PP_PdfAccessibilityAction::PP_PDF_SET_SELECTION;
+    const Selection& sel_action = test_case.action;
+    action_data.selection_start_index.page_index = sel_action.start_page_index;
+    action_data.selection_start_index.char_index = sel_action.start_char_index;
+    action_data.selection_end_index.page_index = sel_action.end_page_index;
+    action_data.selection_end_index.char_index = sel_action.end_char_index;
+    gfx::RectF char_bounds = engine->GetCharBounds(sel_action.start_page_index,
+                                                   sel_action.start_char_index);
+    action_data.target_rect = {{char_bounds.x(), char_bounds.y() + 400 * index},
+                               {char_bounds.width(), char_bounds.height()}};
+
+    engine->HandleAccessibilityAction(action_data);
+    Selection actual_selection;
+    engine->GetSelection(
+        &actual_selection.start_page_index, &actual_selection.start_char_index,
+        &actual_selection.end_page_index, &actual_selection.end_char_index);
+    const Selection& expected_selection = test_case.expected_result;
+    EXPECT_EQ(actual_selection.start_page_index,
+              expected_selection.start_page_index);
+    EXPECT_EQ(actual_selection.start_char_index,
+              expected_selection.start_char_index);
+    EXPECT_EQ(actual_selection.end_page_index,
+              expected_selection.end_page_index);
+    EXPECT_EQ(actual_selection.end_char_index,
+              expected_selection.end_char_index);
+    EXPECT_EQ(test_case.scroll_offset, client.GetScrollRequestDelta());
+    index++;
+  }
+}
+
 }  // namespace chrome_pdf

pdf/pdfium/pdfium_engine.cc

@@ -2180,6 +2180,10 @@ void PDFiumEngine::HandleAccessibilityAction(
           IsPageCharacterIndexInBounds(action_data.selection_end_index)) {
         SetSelection(action_data.selection_start_index,
                      action_data.selection_end_index);
+        gfx::Rect target_rect = RectFromPPRect(action_data.target_rect);
+        if (GetVisibleRect().Contains(target_rect))
+          return;
+        client_->ScrollBy(GetScreenRect(target_rect).OffsetFromOrigin());
       }
       break;
     }