Drop Mohnstrudel tabs into new window when possible

Ash's DragDropController is modified to specially handle drags from the
WebUI tab strip when a flag is enabled. Dropping a tab over an area that
doesn't support accepting the drop will open a new window with only that
tab.

Bug: 1069869
Change-Id: I9ee06a497f8557a3c8e0defff10c8edc1993514c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2130812Reviewed-by: John Lee <johntlee@chromium.org>
Reviewed-by: Mitsuru Oshima <oshima@chromium.org>
Reviewed-by: Xiaoqian Dai <xdai@chromium.org>
Commit-Queue: Collin Baker <collinbaker@chromium.org>
Cr-Commit-Position: refs/heads/master@{#758922}

ash/drag_drop/drag_drop_controller.cc

@@ -9,10 +9,14 @@
 
 #include "ash/drag_drop/drag_drop_tracker.h"
 #include "ash/drag_drop/drag_image_view.h"
+#include "ash/public/cpp/ash_features.h"
 #include "ash/shell.h"
+#include "ash/shell_delegate.h"
 #include "base/bind.h"
 #include "base/metrics/histogram_macros.h"
+#include "base/pickle.h"
 #include "base/run_loop.h"
+#include "base/strings/utf_string_conversions.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "third_party/skia/include/core/SkPath.h"
 #include "ui/aura/client/capture_client.h"
@@ -22,6 +26,8 @@
 #include "ui/aura/window.h"
 #include "ui/aura/window_delegate.h"
 #include "ui/aura/window_event_dispatcher.h"
+#include "ui/base/clipboard/clipboard_format_type.h"
+#include "ui/base/clipboard/custom_data_helper.h"
 #include "ui/base/dragdrop/drag_drop_types.h"
 #include "ui/base/dragdrop/os_exchange_data.h"
 #include "ui/base/hit_test.h"
@@ -466,6 +472,9 @@ void DragDropController::DragUpdate(aura::Window* target,
         cursor = ui::mojom::CursorType::kAlias;
       else if (op & ui::DragDropTypes::DRAG_MOVE)
         cursor = ui::mojom::CursorType::kGrabbing;
+
+      // TODO(https://crbug.com/1069869): don't show kNoDrop cursor for
+      // a tab drag that can drop into a new window.
       Shell::Get()->cursor_manager()->SetCursor(cursor);
     }
   }
@@ -503,15 +512,24 @@ void DragDropController::Drop(aura::Window* target,
   aura::client::DragDropDelegate* delegate =
       aura::client::GetDragDropDelegate(target);
   if (delegate) {
+    const bool is_chrome_tab_drag = IsChromeTabDrag();
+
     ui::DropTargetEvent e(*drag_data_.get(), event.location_f(),
                           event.root_location_f(), drag_operation_);
     e.set_flags(event.flags());
     ui::Event::DispatcherApi(&e).set_target(target);
+
+    ui::OSExchangeData copied_data(drag_data_->provider().Clone());
     drag_operation_ = delegate->OnPerformDrop(e, std::move(drag_data_));
-    if (drag_operation_ == 0)
+    if (drag_operation_ == 0 && is_chrome_tab_drag) {
+      Shell::Get()->shell_delegate()->CreateBrowserForTabDrop(
+          drag_source_window_, copied_data);
+      StartCanceledAnimation(kCancelAnimationDuration);
+    } else if (drag_operation_ == 0) {
       StartCanceledAnimation(kCancelAnimationDuration);
-    else
+    } else {
       drag_image_.reset();
+    }
   } else {
     drag_image_.reset();
   }
@@ -620,4 +638,37 @@ void DragDropController::Cleanup() {
   std::unique_ptr<DragDropTracker> holder = std::move(drag_drop_tracker_);
 }
 
+bool DragDropController::IsChromeTabDrag() {
+  if (!features::IsWebUITabStripTabDragIntegrationEnabled())
+    return false;
+
+  if (!drag_data_)
+    return false;
+  base::Pickle pickle;
+  drag_data_->GetPickledData(ui::ClipboardFormatType::GetWebCustomDataType(),
+                             &pickle);
+  base::PickleIterator iter(pickle);
+
+  uint32_t entry_count = 0;
+  if (!iter.ReadUInt32(&entry_count))
+    return false;
+
+  for (uint32_t i = 0; i < entry_count; ++i) {
+    base::StringPiece16 type;
+    base::StringPiece16 data;
+    if (!iter.ReadStringPiece16(&type) || !iter.ReadStringPiece16(&data)) {
+      return false;
+    }
+
+    // TODO(https://crbug.com/1069869): share this constant between Ash
+    // and Chrome instead of hardcoding it in both places.
+    static const base::string16 chrome_tab_type =
+        base::ASCIIToUTF16("application/vnd.chromium.tab");
+    if (type == chrome_tab_type)
+      return true;
+  }
+
+  return false;
+}
+
 }  // namespace ash

ash/drag_drop/drag_drop_controller.h

@@ -111,6 +111,8 @@ class ASH_EXPORT DragDropController : public aura::client::DragDropClient,
   // Helper method to reset everything.
   void Cleanup();
 
+  bool IsChromeTabDrag();
+
   bool enabled_ = false;
   std::unique_ptr<DragImageView> drag_image_;
   gfx::Vector2d drag_image_offset_;

ash/public/cpp/ash_features.cc

@@ -6,6 +6,7 @@
 
 #include "ash/public/cpp/ash_switches.h"
 #include "base/command_line.h"
+#include "base/feature_list.h"
 #include "build/build_config.h"
 #include "chromeos/constants/chromeos_switches.h"
 
@@ -120,6 +121,9 @@ const base::Feature kHideShelfControlsInTabletMode{
 const base::Feature kSystemTrayMicGainSetting{
     "SystemTrayMicGainSetting", base::FEATURE_DISABLED_BY_DEFAULT};
 
+const base::Feature kWebUITabStripTabDragIntegration{
+    "WebUITabStripTabDragIntegration", base::FEATURE_DISABLED_BY_DEFAULT};
+
 bool IsAllowAmbientEQEnabled() {
   return base::FeatureList::IsEnabled(kAllowAmbientEQ);
 }
@@ -248,6 +252,10 @@ bool IsDisplayIdentificationEnabled() {
   return base::FeatureList::IsEnabled(kDisplayIdentification);
 }
 
+bool IsWebUITabStripTabDragIntegrationEnabled() {
+  return base::FeatureList::IsEnabled(kWebUITabStripTabDragIntegration);
+}
+
 namespace {
 
 // The boolean flag indicating if "WebUITabStrip" feature is enabled in Chrome.

ash/public/cpp/ash_features.h

@@ -154,6 +154,12 @@ ASH_PUBLIC_EXPORT extern const base::Feature kHideShelfControlsInTabletMode;
 // section in the system tray.
 ASH_PUBLIC_EXPORT extern const base::Feature kSystemTrayMicGainSetting;
 
+// Enables special handling of Chrome tab drags from a WebUI tab strip.
+// These will be treated similarly to a window drag, showing split view
+// indicators in tablet mode, etc. The functionality is behind a flag
+// right now since it is under development.
+ASH_PUBLIC_EXPORT extern const base::Feature kWebUITabStripTabDragIntegration;
+
 ASH_PUBLIC_EXPORT bool IsAllowAmbientEQEnabled();
 
 ASH_PUBLIC_EXPORT bool IsAltTabLimitedToActiveDesk();
@@ -210,6 +216,8 @@ ASH_PUBLIC_EXPORT bool IsSystemTrayMicGainSettingEnabled();
 
 ASH_PUBLIC_EXPORT bool IsDisplayIdentificationEnabled();
 
+ASH_PUBLIC_EXPORT bool IsWebUITabStripTabDragIntegrationEnabled();
+
 // These two functions are supposed to be temporary functions to set or get
 // whether "WebUITabStrip" feature is enabled from Chrome.
 ASH_PUBLIC_EXPORT void SetWebUITabStripEnabled(bool enabled);

ash/shell_delegate.cc

@@ -6,6 +6,12 @@
 
 namespace ash {
 
+bool ShellDelegate::CreateBrowserForTabDrop(
+    gfx::NativeWindow source_window,
+    const ui::OSExchangeData& drop_data) {
+  return false;
+}
+
 media_session::mojom::MediaSessionService*
 ShellDelegate::GetMediaSessionService() {
   return nullptr;

ash/shell_delegate.h

@@ -23,6 +23,10 @@ namespace aura {
 class Window;
 }
 
+namespace ui {
+class OSExchangeData;
+}
+
 namespace ash {
 
 class AccessibilityDelegate;
@@ -54,6 +58,9 @@ class ASH_EXPORT ShellDelegate {
   // Check whether the current tab of the browser window can go back.
   virtual bool CanGoBack(gfx::NativeWindow window) const = 0;
 
+  virtual bool CreateBrowserForTabDrop(gfx::NativeWindow source_window,
+                                       const ui::OSExchangeData& drop_data);
+
   // Binds a BluetoothSystemFactory receiver if possible.
   virtual void BindBluetoothSystemFactory(
       mojo::PendingReceiver<device::mojom::BluetoothSystemFactory> receiver) {}

chrome/browser/ui/ash/chrome_shell_delegate.cc

@@ -6,6 +6,7 @@
 
 #include <memory>
 
+#include "ash/public/cpp/ash_features.h"
 #include "ash/screenshot_delegate.h"
 #include "base/bind.h"
 #include "chrome/browser/browser_process.h"
@@ -26,6 +27,7 @@
 #include "chrome/browser/ui/browser_window.h"
 #include "chrome/browser/ui/scoped_tabbed_browser_displayer.h"
 #include "chrome/browser/ui/views/frame/browser_view.h"
+#include "chrome/browser/ui/webui/tab_strip/tab_strip_ui_util.h"
 #include "chromeos/services/multidevice_setup/multidevice_setup_service.h"
 #include "content/public/browser/device_service.h"
 #include "content/public/browser/media_session_service.h"
@@ -71,6 +73,36 @@ bool ChromeShellDelegate::CanGoBack(gfx::NativeWindow window) const {
   return contents->GetController().CanGoBack();
 }
 
+bool ChromeShellDelegate::CreateBrowserForTabDrop(
+    gfx::NativeWindow source_window,
+    const ui::OSExchangeData& drop_data) {
+  CHECK(ash::features::IsWebUITabStripTabDragIntegrationEnabled());
+
+  BrowserView* source_view = BrowserView::GetBrowserViewForNativeWindow(
+      source_window->GetToplevelWindow());
+  if (!source_view)
+    return false;
+
+  Browser::CreateParams params = source_view->browser()->create_params();
+  params.user_gesture = true;
+  params.initial_show_state = ui::SHOW_STATE_DEFAULT;
+  Browser* browser = Browser::Create(params);
+  if (!browser)
+    return false;
+
+  if (!tab_strip_ui::DropTabsInNewBrowser(browser, drop_data)) {
+    browser->window()->Close();
+    return false;
+  }
+
+  // TODO(https://crbug.com/1069869): evaluate whether the above
+  // failures can happen in valid states, and if so whether we need to
+  // reflect failure in UX.
+
+  browser->window()->Show();
+  return true;
+}
+
 void ChromeShellDelegate::BindBluetoothSystemFactory(
     mojo::PendingReceiver<device::mojom::BluetoothSystemFactory> receiver) {
   content::GetDeviceService().BindBluetoothSystemFactory(std::move(receiver));

chrome/browser/ui/ash/chrome_shell_delegate.h

@@ -22,6 +22,8 @@ class ChromeShellDelegate : public ash::ShellDelegate {
       ash::BackGestureContextualNudgeController* controller) override;
   void OpenKeyboardShortcutHelpPage() const override;
   bool CanGoBack(gfx::NativeWindow window) const override;
+  bool CreateBrowserForTabDrop(gfx::NativeWindow source_window,
+                               const ui::OSExchangeData& drop_data) override;
   void BindBluetoothSystemFactory(
       mojo::PendingReceiver<device::mojom::BluetoothSystemFactory> receiver)
       override;

chrome/browser/ui/webui/tab_strip/tab_strip_ui_util.cc

@@ -4,12 +4,19 @@
 
 #include "chrome/browser/ui/webui/tab_strip/tab_strip_ui_util.h"
 
+#include "base/strings/string_number_conversions.h"
+#include "base/strings/utf_string_conversions.h"
+#include "chrome/browser/extensions/extension_tab_util.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/ui/browser.h"
 #include "chrome/browser/ui/browser_list.h"
 #include "chrome/browser/ui/tabs/tab_group_model.h"
+#include "chrome/browser/ui/webui/tab_strip/tab_strip_ui.h"
 #include "components/tab_groups/tab_group_id.h"
 #include "content/public/browser/web_contents.h"
+#include "ui/base/clipboard/clipboard_format_type.h"
+#include "ui/base/clipboard/custom_data_helper.h"
+#include "ui/base/dragdrop/os_exchange_data.h"
 
 namespace tab_strip_ui {
 
@@ -65,4 +72,37 @@ void MoveTabAcrossWindows(Browser* source_browser,
       to_index, std::move(detached_contents), add_types, to_group_id);
 }
 
+bool DropTabsInNewBrowser(Browser* new_browser,
+                          const ui::OSExchangeData& drop_data) {
+  base::Pickle pickle;
+  drop_data.GetPickledData(ui::ClipboardFormatType::GetWebCustomDataType(),
+                           &pickle);
+
+  base::string16 tab_id_str;
+  ui::ReadCustomDataForType(pickle.data(), pickle.size(),
+                            base::ASCIIToUTF16(kWebUITabIdDataType),
+                            &tab_id_str);
+  if (tab_id_str.empty())
+    return false;
+
+  // |tab_id_str| should contain the extension tab id as a string.
+  int tab_id = -1;
+  if (!base::StringToInt(tab_id_str, &tab_id))
+    return false;
+
+  Browser* source_browser = nullptr;
+  int source_index = -1;
+  if (!extensions::ExtensionTabUtil::GetTabById(
+          tab_id, new_browser->profile(), /* include_incognito = */ false,
+          &source_browser, /* tab_strip = */ nullptr,
+          /* contents = */ nullptr, &source_index)) {
+    return false;
+  }
+
+  MoveTabAcrossWindows(source_browser, source_index, new_browser, 0,
+                       base::nullopt);
+  new_browser->tab_strip_model()->ActivateTabAt(0);
+  return true;
+}
+
 }  // namespace tab_strip_ui

chrome/browser/ui/webui/tab_strip/tab_strip_ui_util.h

@@ -12,6 +12,10 @@ class Browser;
 class Profile;
 class TabGroupModel;
 
+namespace ui {
+class OSExchangeData;
+}
+
 namespace tab_strip_ui {
 
 base::Optional<tab_groups::TabGroupId> GetTabGroupIdFromString(
@@ -27,6 +31,15 @@ void MoveTabAcrossWindows(
     int to_index,
     base::Optional<tab_groups::TabGroupId> to_group_id = base::nullopt);
 
+// Handles dropping tabs not destined for an existing tab strip.
+// |new_browser| should be the newly created Browser with no tabs, and
+// must have the same profile as the drag source. |drop_data| must have
+// originated from a drag in a WebUI tab strip. If successful, the tabs
+// reflected in |drop_data| will be moved from the source browser to
+// |new_browser|.
+bool DropTabsInNewBrowser(Browser* new_browser,
+                          const ui::OSExchangeData& drop_data);
+
 }  // namespace tab_strip_ui
 
 #endif  // CHROME_BROWSER_UI_WEBUI_TAB_STRIP_TAB_STRIP_UI_UTIL_H_