Clipboard: Make ClipboardObserver virtual functions default-passthrough.

Observer interfaces having default-passthrough virtual methods rather
than pure virtual methods allows observers to only override functions
they'd make use of, and not have to override other functions.

This was inspired by: https://chromium-review.googlesource.com/c/chromium/src/+/2341407/33#message-8c9e7fa5cb0118798e3bd2f92bbe1cfe37a85640

Change-Id: I2e4e852204322a4608b4e449e0f7e9ab7e73f870
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2382959Reviewed-by: Scott Violet <sky@chromium.org>
Commit-Queue: Darwin Huang <huangdarwin@chromium.org>
Auto-Submit: Darwin Huang <huangdarwin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#804474}

ash/clipboard/clipboard_history.cc

@@ -105,8 +105,6 @@ void ClipboardHistory::OnClipboardDataChanged() {
                      commit_data_weak_factory_.GetWeakPtr(), *clipboard_data));
 }
 
-void ClipboardHistory::OnClipboardDataRead() {}
-
 void ClipboardHistory::MaybeCommitData(ui::ClipboardData data) {
   if (!ClipboardHistoryUtil::IsSupported(data))
     return;

ash/clipboard/clipboard_history.h

@@ -72,7 +72,6 @@ class ASH_EXPORT ClipboardHistory : public ui::ClipboardObserver {
 
   // ClipboardMonitor:
   void OnClipboardDataChanged() override;
-  void OnClipboardDataRead() override;
 
  private:
   // Adds `data` to the `history_list_` if it's supported. If `data` is not

ash/clipboard/clipboard_nudge_controller.cc

@@ -63,8 +63,6 @@ void ClipboardNudgeController::OnClipboardHistoryItemAdded(
   }
 }
 
-void ClipboardNudgeController::OnClipboardDataChanged() {}
-
 void ClipboardNudgeController::OnClipboardDataRead() {
   PrefService* prefs =
       Shell::Get()->session_controller()->GetLastActiveUserPrefService();

ash/clipboard/clipboard_nudge_controller.h

@@ -42,7 +42,6 @@ class ASH_EXPORT ClipboardNudgeController : public ClipboardHistory::Observer,
   void OnClipboardHistoryItemAdded(const ClipboardHistoryItem& item) override;
 
   // ui::ClipboardObserver:
-  void OnClipboardDataChanged() override;
   void OnClipboardDataRead() override;
 
   // Resets nudge state and show nudge timer.

chrome/browser/chromeos/extensions/autotest_private/autotest_private_api.h

@@ -735,7 +735,6 @@ class AutotestPrivateAPI : public BrowserContextKeyedAPI,
 
   // ui::ClipboardObserver
   void OnClipboardDataChanged() override;
-  void OnClipboardDataRead() override {}
 
   ScopedObserver<ui::ClipboardMonitor, ui::ClipboardObserver>
       clipboard_observer_;

chrome/browser/pdf/pdf_extension_test.cc

@@ -2032,9 +2032,6 @@ class PDFExtensionClipboardTest : public PDFExtensionTestWithParam,
     clipboard_changed_ = true;
     std::move(clipboard_quit_closure_).Run();
   }
-#if defined(OS_CHROMEOS)
-  void OnClipboardDataRead() override {}
-#endif
 
   void LoadTestComboBoxPdfGetGuestContents() {
     GURL test_pdf_url(embedded_test_server()->GetURL("/pdf/combobox_form.pdf"));

chrome/browser/sharing/shared_clipboard/remote_copy_message_handler_unittest.cc

@@ -56,9 +56,6 @@ class ClipboardObserver : public ui::ClipboardObserver {
 
   // ui::ClipboardObserver:
   void OnClipboardDataChanged() override { callback_.Run(); }
-#if defined(OS_CHROMEOS)
-  void OnClipboardDataRead() override {}
-#endif
 
  private:
   base::RepeatingClosure callback_;

chrome/browser/ui/ash/chrome_screenshot_grabber_browsertest.cc

@@ -78,7 +78,6 @@ class ChromeScreenshotGrabberBrowserTest
     clipboard_changed_ = true;
     message_loop_runner_->Quit();
   }
-  void OnClipboardDataRead() override {}
 
   void RunLoop() {
     message_loop_runner_ = new content::MessageLoopRunner;

chrome/browser/ui/views/sharing/remote_copy_browsertest.cc

@@ -55,9 +55,6 @@ class ClipboardObserver : public ui::ClipboardObserver {
       : callback_(callback) {}
 
   void OnClipboardDataChanged() override { callback_.Run(); }
-#if defined(OS_CHROMEOS)
-  void OnClipboardDataRead() override {}
-#endif
 
  private:
   base::RepeatingClosure callback_;

components/arc/clipboard/arc_clipboard_bridge.h

@@ -36,7 +36,6 @@ class ArcClipboardBridge : public KeyedService,
 
   // ClipboardObserver overrides.
   void OnClipboardDataChanged() override;
-  void OnClipboardDataRead() override {}
 
   // mojom::ClipboardHost overrides.
   void SetClipContent(mojom::ClipDataPtr clip_data) override;

components/exo/data_device.h

@@ -8,7 +8,6 @@
 #include <cstdint>
 
 #include "base/macros.h"
-#include "build/build_config.h"
 #include "components/exo/data_offer_observer.h"
 #include "components/exo/seat_observer.h"
 #include "components/exo/surface.h"
@@ -67,9 +66,6 @@ class DataDevice : public WMHelper::DragDropObserver,
 
   // Overridden from ui::ClipboardObserver:
   void OnClipboardDataChanged() override;
-#if defined(OS_CHROMEOS)
-  void OnClipboardDataRead() override {}
-#endif
 
   // Overridden from SeatObserver:
   void OnSurfaceFocusing(Surface* surface) override;

components/exo/seat.h

@@ -8,7 +8,6 @@
 #include "base/containers/flat_map.h"
 #include "base/memory/weak_ptr.h"
 #include "base/observer_list.h"
-#include "build/build_config.h"
 #include "components/exo/data_source_observer.h"
 #include "ui/aura/client/drag_drop_delegate.h"
 #include "ui/aura/client/focus_change_observer.h"
@@ -99,9 +98,6 @@ class Seat : public aura::client::FocusChangeObserver,
 
   // Overridden from ui::ClipboardObserver:
   void OnClipboardDataChanged() override;
-#if defined(OS_CHROMEOS)
-  void OnClipboardDataRead() override {}
-#endif  // defined(OS_CHROMEOS)
 
   // Overridden from DataSourceObserver:
   void OnDataSourceDestroying(DataSource* source) override;

extensions/browser/api/clipboard/clipboard_api.h

@@ -7,7 +7,6 @@
 
 #include <vector>
 
-#include "build/build_config.h"
 #include "extensions/browser/browser_context_keyed_api_factory.h"
 #include "extensions/browser/extension_function.h"
 #include "extensions/common/api/clipboard.h"
@@ -28,9 +27,6 @@ class ClipboardAPI : public BrowserContextKeyedAPI,
 
   // ui::ClipboardObserver implementation.
   void OnClipboardDataChanged() override;
-#if defined(OS_CHROMEOS)
-  void OnClipboardDataRead() override {}
-#endif
 
  private:
   friend class BrowserContextKeyedAPIFactory<ClipboardAPI>;

ui/base/clipboard/BUILD.gn

@@ -72,6 +72,7 @@ component("clipboard") {
     "clipboard_metrics.h",
     "clipboard_monitor.cc",
     "clipboard_monitor.h",
+    "clipboard_observer.cc",
     "clipboard_observer.h",
     "custom_data_helper.cc",
     "custom_data_helper.h",

ui/base/clipboard/clipboard_observer.cc

+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "ui/base/clipboard/clipboard_observer.h"
+
+namespace ui {
+
+void ClipboardObserver::OnClipboardDataChanged() {}
+
+#if defined(OS_CHROMEOS)
+void ClipboardObserver::OnClipboardDataRead() {}
+#endif
+
+ClipboardObserver::~ClipboardObserver() = default;
+
+}  // namespace ui

ui/base/clipboard/clipboard_observer.h

@@ -11,19 +11,19 @@
 
 namespace ui {
 
-// Observer that receives the notifications of clipboard change events.
+// Observer that receives the notifications of clipboard events.
 class COMPONENT_EXPORT(UI_BASE_CLIPBOARD) ClipboardObserver {
  public:
-  // Called when clipboard data is changed.
-  virtual void OnClipboardDataChanged() = 0;
+  // Override notified when clipboard data is changed.
+  virtual void OnClipboardDataChanged();
 
 #if defined(OS_CHROMEOS)
-  // Called when clipboard data is read.
-  virtual void OnClipboardDataRead() = 0;
+  // Override notified when clipboard data is read.
+  virtual void OnClipboardDataRead();
 #endif
 
  protected:
-  virtual ~ClipboardObserver() = default;
+  virtual ~ClipboardObserver();
 };
 
 }  // namespace ui