Revert "Delivers drag and drop methods from Surface to DataDevice."

This reverts commit c59f6260.

Reason for revert: Broke compilation on Linux ChromiumOS Builder (dbg)

../../components/exo/data_device_delegate.h:28: error: undefined reference to 'vtable for exo::DataDeviceDelegate'
../../third_party/binutils/Linux_x64/Release/bin/ld.gold: the vtable symbol may be undefined because the class is missing its key function
clang: error: linker command failed with exit code 1 (use -v to see invocation)

Original change's description:
> Delivers drag and drop methods from Surface to DataDevice.
> 
> The CL lets Surface observe drag and drop events and delegates the events to
> DataDevice thorugh DataDeviceManager.
> 
> Bug: b:31988797
> Test: None
> Change-Id: I9574cd86137922d7527bd297d182a7b45e632c9e
> Reviewed-on: https://chromium-review.googlesource.com/579250
> Commit-Queue: Daichi Hirono <hirono@chromium.org>
> Reviewed-by: David Reveman <reveman@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#491951}

TBR=reveman@chromium.org,hirono@chromium.org,hidehiko@chromium.org

Change-Id: Ie770510e27a19b94f5e621ef41d24138c219104c
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: b:31988797
Reviewed-on: https://chromium-review.googlesource.com/601989Reviewed-by: Vasilii Sukhanov <vasilii@chromium.org>
Commit-Queue: Vasilii Sukhanov <vasilii@chromium.org>
Cr-Commit-Position: refs/heads/master@{#491984}

components/exo/data_device.cc

@@ -6,19 +6,13 @@
 
 #include "base/logging.h"
 #include "components/exo/data_device_delegate.h"
-#include "components/exo/surface.h"
-#include "ui/base/dragdrop/drag_drop_types.h"
-#include "ui/base/dragdrop/drop_target_event.h"
 
 namespace exo {
 
-DataDevice::DataDevice(DataDeviceDelegate* delegate) : delegate_(delegate) {
-  WMHelper::GetInstance()->AddDragDropObserver(this);
-}
+DataDevice::DataDevice(DataDeviceDelegate* delegate) : delegate_(delegate) {}
 
 DataDevice::~DataDevice() {
   delegate_->OnDataDeviceDestroying(this);
-  WMHelper::GetInstance()->RemoveDragDropObserver(this);
 }
 
 void DataDevice::StartDrag(const DataSource* source_resource,
@@ -34,32 +28,4 @@ void DataDevice::SetSelection(const DataSource* source, uint32_t serial) {
   NOTIMPLEMENTED();
 }
 
-void DataDevice::OnDragEntered(const ui::DropTargetEvent& event) {
-  NOTIMPLEMENTED();
-}
-
-int DataDevice::OnDragUpdated(const ui::DropTargetEvent& event) {
-  NOTIMPLEMENTED();
-  return ui::DragDropTypes::DRAG_NONE;
-}
-
-void DataDevice::OnDragExited() {
-  NOTIMPLEMENTED();
-}
-
-int DataDevice::OnPerformDrop(const ui::DropTargetEvent& event) {
-  NOTIMPLEMENTED();
-  return ui::DragDropTypes::DRAG_NONE;
-}
-
-Surface* DataDevice::GetEffectiveTargetForEvent(
-    const ui::DropTargetEvent& event) const {
-  Surface* target =
-      Surface::AsSurface(static_cast<aura::Window*>(event.target()));
-  if (!target)
-    return nullptr;
-
-  return delegate_->CanAcceptDataEventsForSurface(target) ? target : nullptr;
-}
-
 }  // namespace exo

components/exo/data_device.h

@@ -8,11 +8,6 @@
 #include <cstdint>
 
 #include "base/macros.h"
-#include "components/exo/wm_helper.h"
-
-namespace ui {
-class DropTargetEvent;
-}
 
 namespace exo {
 
@@ -24,10 +19,10 @@ enum class DndAction { kNone, kCopy, kMove, kAsk };
 
 // Data transfer device providing access to inter-client data transfer
 // mechanisms such as copy-and-paste and drag-and-drop.
-class DataDevice : public WMHelper::DragDropObserver {
+class DataDevice {
  public:
   explicit DataDevice(DataDeviceDelegate* delegate);
-  ~DataDevice() override;
+  ~DataDevice();
 
   // Starts drag-and-drop operation.
   // |source| is data source for the eventual transfer or null if data passing
@@ -44,15 +39,7 @@ class DataDevice : public WMHelper::DragDropObserver {
   // selection. |serial| is a unique number of event which tigers SetSelection.
   void SetSelection(const DataSource* source, uint32_t serial);
 
-  // Overridden from WMHelper::DragDropObserver:
-  void OnDragEntered(const ui::DropTargetEvent& event) override;
-  int OnDragUpdated(const ui::DropTargetEvent& event) override;
-  void OnDragExited() override;
-  int OnPerformDrop(const ui::DropTargetEvent& event) override;
-
  private:
-  Surface* GetEffectiveTargetForEvent(const ui::DropTargetEvent& event) const;
-
   DataDeviceDelegate* const delegate_;
 
   DISALLOW_COPY_AND_ASSIGN(DataDevice);

components/exo/data_device_delegate.h

@@ -57,10 +57,6 @@ class DataDeviceDelegate {
   // Called when the data is pasted on the DataDevice.
   virtual void OnSelection(const DataOffer& data_offer) = 0;
 
-  // This should return true if |surface| is a valid target for this data
-  // device. E.g. the surface is owned by the same client as the data device.
-  virtual bool CanAcceptDataEventsForSurface(Surface* surface);
-
  protected:
   virtual ~DataDeviceDelegate() {}
 };

components/exo/wayland/server.cc

@@ -2843,10 +2843,6 @@ class WaylandDataDeviceDelegate : public DataDeviceDelegate {
 
   // Overridden from DataDeviceDelegate:
   void OnDataDeviceDestroying(DataDevice* device) override { delete this; }
-  bool CanAcceptDataEventsForSurface(Surface* surface) override {
-    return surface &&
-           wl_resource_get_client(GetSurfaceResource(surface)) == client_;
-  }
   class DataOffer* OnDataOffer(const std::vector<std::string>& mime_types,
                                const base::flat_set<DndAction>& source_actions,
                                DndAction dnd_action) override {