Forward tab events to PDF plugin from blink

Blink brings plugin to focus but does not forward the tab event to
plugin. Simulating tab to enable seamless tabbing across UI and plugin.

Bug: 989046
Change-Id: Ie156c66a25a87afe9b56083f98876cc6e75917e9
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2061636
Reviewed-by: Alex Moshchuk <alexmos@chromium.org>
Reviewed-by: Jochen Eisinger <jochen@chromium.org>
Reviewed-by: Lei Zhang <thestig@chromium.org>
Reviewed-by: Yoshifumi Inoue <yosin@chromium.org>
Reviewed-by: Kevin Babbitt <kbabbitt@microsoft.com>
Commit-Queue: Ankit Kumar 🌪️ <ankk@microsoft.com>
Cr-Commit-Position: refs/heads/master@{#761853}

chrome/browser/pdf/pdf_extension_test.cc

@@ -2418,6 +2418,44 @@ IN_PROC_BROWSER_TEST_F(PDFExtensionTest, Metrics) {
   EXPECT_EQ(1, actions.GetActionCount("PDF.LoadSuccess"));
 }
 
+IN_PROC_BROWSER_TEST_F(PDFExtensionTest, TabInAndOutOfPDFPlugin) {
+  GURL test_pdf_url(embedded_test_server()->GetURL("/pdf/test.pdf"));
+  content::WebContents* guest_contents = LoadPdfGetGuestContents(test_pdf_url);
+  ASSERT_TRUE(guest_contents);
+
+  // Set focus on PDF document.
+  ASSERT_TRUE(content::ExecuteScript(
+      guest_contents, "document.getElementById('plugin').focus();"));
+
+  // The script will ensure we return the id of the focused element on focus.
+  std::string script =
+      "function onFocus(e) {"
+      "  domAutomationController.send(e.target.id);"
+      "}"
+      "const plugin = document.getElementById('plugin');"
+      "const button = "
+      "document.getElementById('zoom-toolbar').$['zoom-out-button'];"
+      "plugin.addEventListener('focus', onFocus);"
+      "button.addEventListener('focus', onFocus);";
+  ASSERT_TRUE(content::ExecuteScript(guest_contents, script));
+
+  // Helper to simulate a tab press and wait for a focus message.
+  auto press_tab_and_wait_for_message = [guest_contents](bool reverse) {
+    content::DOMMessageQueue msg_queue;
+    std::string reply;
+    SimulateKeyPress(guest_contents, ui::DomKey::TAB, ui::DomCode::TAB,
+                     ui::VKEY_TAB, false, /*shift=*/reverse, false, false);
+    EXPECT_TRUE(msg_queue.WaitForMessage(&reply));
+    return reply;
+  };
+
+  // Press <shift-tab> and ensure that last toolbar element (zoom-out-button)
+  // receives focus.
+  EXPECT_EQ("\"zoom-out-button\"", press_tab_and_wait_for_message(true));
+  // Press <tab> and ensure that PDF document receives focus.
+  EXPECT_EQ("\"plugin\"", press_tab_and_wait_for_message(false));
+}
+
 // This test suite does a simple text-extraction based on the accessibility
 // internals, breaking lines & paragraphs where appropriate.  Unlike
 // TreeDumpTests, this allows us to verify the kNextOnLine and kPreviousOnLine

content/renderer/DEPS

@@ -31,6 +31,7 @@ include_rules = [
   "+third_party/hyphen/hyphen.h",
   "+third_party/webrtc_overrides",
   "+third_party/blink/public/common",
+  "+third_party/blink/public/mojom",
   "+v8/include",
   "+v8/src/third_party/vtune",
 ]

content/renderer/pepper/DEPS

@@ -9,4 +9,5 @@ include_rules = [
   "+third_party/opus",
   "+ui/base/ime",
   "+ui/base/range",
+  "+ui/events/keycodes/keyboard_codes.h",
 ]

content/renderer/pepper/pepper_plugin_instance_impl.cc

@@ -2229,6 +2229,11 @@ void PepperPluginInstanceImpl::OnHiddenForPlaceholder(bool hidden) {
   UpdateLayer(false /* device_changed */);
 }
 
+bool PepperPluginInstanceImpl::SupportsKeyboardFocus() {
+  // Only PDF plugin supports keyboard focus.
+  return LoadPdfInterface();
+}
+
 void PepperPluginInstanceImpl::AddPluginObject(PluginObject* plugin_object) {
   DCHECK(live_plugin_objects_.find(plugin_object) ==
          live_plugin_objects_.end());

content/renderer/pepper/pepper_plugin_instance_impl.h

@@ -522,6 +522,8 @@ class CONTENT_EXPORT PepperPluginInstanceImpl
   // Should be used only for logging.
   bool is_flash_plugin() const { return is_flash_plugin_; }
 
+  bool SupportsKeyboardFocus();
+
  private:
   friend class base::RefCounted<PepperPluginInstanceImpl>;
   friend class PpapiPluginInstanceTest;

content/renderer/pepper/pepper_webplugin_impl.cc

@@ -13,6 +13,7 @@
 #include "base/single_thread_task_runner.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/threading/thread_task_runner_handle.h"
+#include "base/time/time.h"
 #include "content/public/renderer/content_renderer_client.h"
 #include "content/renderer/pepper/message_channel.h"
 #include "content/renderer/pepper/pepper_plugin_instance_impl.h"
@@ -23,7 +24,10 @@
 #include "content/renderer/renderer_blink_platform_impl.h"
 #include "ppapi/shared_impl/ppapi_globals.h"
 #include "ppapi/shared_impl/var_tracker.h"
+#include "third_party/blink/public/common/input/web_input_event.h"
+#include "third_party/blink/public/common/input/web_keyboard_event.h"
 #include "third_party/blink/public/common/thread_safe_browser_interface_broker_proxy.h"
+#include "third_party/blink/public/mojom/input/focus_type.mojom.h"
 #include "third_party/blink/public/platform/platform.h"
 #include "third_party/blink/public/platform/web_coalesced_input_event.h"
 #include "third_party/blink/public/platform/web_rect.h"
@@ -37,6 +41,8 @@
 #include "third_party/blink/public/web/web_print_params.h"
 #include "third_party/blink/public/web/web_print_preset_options.h"
 #include "third_party/blink/public/web/web_print_scaling_option.h"
+#include "ui/base/cursor/cursor.h"
+#include "ui/events/keycodes/keyboard_codes.h"
 #include "url/gurl.h"
 
 using ppapi::V8ObjectVar;
@@ -187,6 +193,10 @@ v8::Local<v8::Object> PepperWebPluginImpl::V8ScriptableObject(
   return result;
 }
 
+bool PepperWebPluginImpl::SupportsKeyboardFocus() const {
+  return instance_ && instance_->SupportsKeyboardFocus();
+}
+
 void PepperWebPluginImpl::Paint(cc::PaintCanvas* canvas, const WebRect& rect) {
   // Re-entrancy may cause JS to try to execute script on the plugin before it
   // is fully initialized. See: crbug.com/715747.
@@ -208,8 +218,23 @@ void PepperWebPluginImpl::UpdateFocus(bool focused,
                                       blink::mojom::FocusType focus_type) {
   // Re-entrancy may cause JS to try to execute script on the plugin before it
   // is fully initialized. See: crbug.com/715747.
-  if (instance_)
+  if (instance_) {
     instance_->SetWebKitFocus(focused);
+
+    if (focused && instance_->SupportsKeyboardFocus()) {
+      int modifiers = blink::WebInputEvent::kNoModifiers;
+      if (focus_type == blink::mojom::FocusType::kBackward)
+        modifiers |= blink::WebInputEvent::kShiftKey;
+      // As part of focus management for plugin, blink brings plugin to focus
+      // but does not forward the tab event to plugin. Hence simulating tab
+      // event here to enable seamless tabbing across UI & plugin.
+      blink::WebKeyboardEvent simulated_event(blink::WebInputEvent::kKeyDown,
+                                              modifiers, base::TimeTicks());
+      simulated_event.windows_key_code = ui::KeyboardCode::VKEY_TAB;
+      ui::Cursor cursor;
+      instance_->HandleInputEvent(simulated_event, &cursor);
+    }
+  }
 }
 
 void PepperWebPluginImpl::UpdateVisibility(bool visible) {}

content/renderer/pepper/pepper_webplugin_impl.h

@@ -45,6 +45,7 @@ class PepperWebPluginImpl : public blink::WebPlugin {
   bool Initialize(blink::WebPluginContainer* container) override;
   void Destroy() override;
   v8::Local<v8::Object> V8ScriptableObject(v8::Isolate* isolate) override;
+  bool SupportsKeyboardFocus() const override;
   void UpdateAllLifecyclePhases(blink::DocumentUpdateReason) override {}
   void Paint(cc::PaintCanvas* canvas, const blink::WebRect& rect) override;
   void UpdateGeometry(const blink::WebRect& window_rect,

third_party/blink/renderer/core/html/html_plugin_element.cc

@@ -483,7 +483,7 @@ bool HTMLPlugInElement::IsKeyboardFocusable() const {
   if (HTMLFrameOwnerElement::IsKeyboardFocusable())
     return true;
   return GetDocument().IsActive() && PluginEmbeddedContentView() &&
-         PluginEmbeddedContentView()->SupportsKeyboardFocus();
+         PluginEmbeddedContentView()->SupportsKeyboardFocus() && IsFocusable();
 }
 
 bool HTMLPlugInElement::HasCustomFocusLogic() const {

third_party/blink/web_tests/plugins/focus-expected.txt

@@ -2,6 +2,7 @@ CONSOLE MESSAGE: Blink Test Plugin: initializing
 CONSOLE MESSAGE: Blink Test Plugin: initializing
 CONSOLE MESSAGE: Blink Test Plugin: initializing
 CONSOLE MESSAGE: Blink Test Plugin: initializing
+CONSOLE MESSAGE: Blink Test Plugin: DidChangeFocus(true)
 Test for Embed and Object for bug 32292: Unable to focus on embedded plugins such as Flash via javascript focus().
 
 On success, you will see a series of "PASS" messages, followed by "TEST COMPLETE".