Convert NULL to nullptr or shorten to bool-like expression

https://google.github.io/styleguide/cppguide.html#0_and_nullptr/NULL
says:
"For pointers (address values), use nullptr, as this provides
type-safety."
Furthermore, NULL/0 won't compile if we change |SomeClass*| to
|CheckedPtr<SomeClass>|. See go/miracleptr for more details.

!! is used in situations where the pointer is assigned to or returned
as bool, otherwise CheckedPtr's more costly implicit T* cast operator
would kick in. !! isn't needed in boolean expressions. Examples here:
https://chromium-review.googlesource.com/c/chromium/src/+/2226003

Bug: 1080832
Change-Id: I449817c8949d85bd99a1f7d5043cd189f109303c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2227936
Auto-Submit: Bartek Nowierski <bartekn@chromium.org>
Commit-Queue: Kentaro Hara <haraken@chromium.org>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Cr-Commit-Position: refs/heads/master@{#774523}

chrome/browser/ui/views/tabs/tab_drag_controller.cc

@@ -70,7 +70,7 @@ using content::OpenURLParams;
 using content::WebContents;
 
 // If non-null there is a drag underway.
-static TabDragController* g_tab_drag_controller = NULL;
+static TabDragController* g_tab_drag_controller = nullptr;
 
 namespace {
 
@@ -408,7 +408,7 @@ TabDragController::TabDragController()
 
 TabDragController::~TabDragController() {
   if (g_tab_drag_controller == this)
-    g_tab_drag_controller = NULL;
+    g_tab_drag_controller = nullptr;
 
   if (move_loop_widget_)
     move_loop_widget_->RemoveObserver(this);
@@ -1320,7 +1320,7 @@ void TabDragController::Detach(ReleaseCapture release_capture) {
 
   ClearTabDraggingInfo();
   attached_context_->DraggedTabsDetached();
-  attached_context_ = NULL;
+  attached_context_ = nullptr;
   attached_views_.clear();
 }
 
@@ -1441,7 +1441,7 @@ void TabDragController::RunMoveLoop(const gfx::Vector2d& drag_offset) {
     // Activate may trigger a focus loss, destroying us.
     if (!ref)
       return;
-    tab_strip_to_attach_to_after_exit_ = NULL;
+    tab_strip_to_attach_to_after_exit_ = nullptr;
   } else if (current_state_ == DragState::kWaitingToStop) {
     EndDrag(result == views::Widget::MOVE_LOOP_CANCELED ? END_DRAG_CANCEL
                                                         : END_DRAG_COMPLETE);

services/audio/output_controller.cc

@@ -530,7 +530,7 @@ void OutputController::StopCloseAndClearStream() {
     stream_->Close();
     stats_tracker_.reset();
 
-    stream_ = NULL;
+    stream_ = nullptr;
   }
 
   state_ = kEmpty;

ui/aura/window_event_dispatcher.cc

@@ -53,7 +53,7 @@ bool IsNonClientLocation(Window* target, const gfx::Point& location) {
 }
 
 Window* ConsumerToWindow(ui::GestureConsumer* consumer) {
-  return consumer ? static_cast<Window*>(consumer) : NULL;
+  return consumer ? static_cast<Window*>(consumer) : nullptr;
 }
 
 bool IsEventCandidateForHold(const ui::Event& event) {
@@ -150,7 +150,7 @@ void WindowEventDispatcher::DispatchCancelModeEvent() {
   ui::CancelModeEvent event;
   Window* focused_window = client::GetFocusClient(window())->GetFocusedWindow();
   if (focused_window && !window()->Contains(focused_window))
-    focused_window = NULL;
+    focused_window = nullptr;
   DispatchDetails details =
       DispatchEvent(focused_window ? focused_window : window(), &event);
   if (details.dispatcher_destroyed)
@@ -246,8 +246,8 @@ gfx::Point WindowEventDispatcher::GetLastMouseLocationInRoot() const {
 }
 
 void WindowEventDispatcher::OnHostLostMouseGrab() {
-  mouse_pressed_handler_ = NULL;
-  mouse_moved_handler_ = NULL;
+  mouse_pressed_handler_ = nullptr;
+  mouse_moved_handler_ = nullptr;
 }
 
 void WindowEventDispatcher::OnCursorMovedToRootLocation(
@@ -358,9 +358,9 @@ void WindowEventDispatcher::OnWindowHidden(Window* invisible,
   // If the window the mouse was pressed in becomes invisible, it should no
   // longer receive mouse events.
   if (invisible->Contains(mouse_pressed_handler_))
-    mouse_pressed_handler_ = NULL;
+    mouse_pressed_handler_ = nullptr;
   if (invisible->Contains(mouse_moved_handler_))
-    mouse_moved_handler_ = NULL;
+    mouse_moved_handler_ = nullptr;
   if (invisible->Contains(touchpad_pinch_handler_))
     touchpad_pinch_handler_ = nullptr;
 
@@ -369,7 +369,7 @@ void WindowEventDispatcher::OnWindowHidden(Window* invisible,
   // dispatching events in the inner loop, then reset the target for the outer
   // loop.
   if (invisible->Contains(old_dispatch_target_))
-    old_dispatch_target_ = NULL;
+    old_dispatch_target_ = nullptr;
 
   invisible->CleanupGestureState();
 
@@ -384,10 +384,10 @@ void WindowEventDispatcher::OnWindowHidden(Window* invisible,
     client::CaptureClient* capture_client =
         client::GetCaptureClient(host_->window());
     Window* capture_window =
-        capture_client ? capture_client->GetCaptureWindow() : NULL;
+        capture_client ? capture_client->GetCaptureWindow() : nullptr;
 
     if (invisible->Contains(event_dispatch_target_))
-      event_dispatch_target_ = NULL;
+      event_dispatch_target_ = nullptr;
 
     // If the ancestor of the capture window is hidden, release the capture.
     // Note that this may delete the window so do not use capture_window
@@ -411,7 +411,7 @@ void WindowEventDispatcher::UpdateCapture(Window* old_capture,
   // (see below). Clear it here to ensure we don't end up referencing a stale
   // Window.
   if (mouse_moved_handler_ && !window()->Contains(mouse_moved_handler_))
-    mouse_moved_handler_ = NULL;
+    mouse_moved_handler_ = nullptr;
 
   if (old_capture && old_capture->GetRootWindow() == window() &&
       old_capture->delegate()) {
@@ -439,7 +439,7 @@ void WindowEventDispatcher::UpdateCapture(Window* old_capture,
     if (details.dispatcher_destroyed)
       return;
   }
-  mouse_pressed_handler_ = NULL;
+  mouse_pressed_handler_ = nullptr;
 }
 
 void WindowEventDispatcher::OnOtherRootGotCapture() {
@@ -461,8 +461,8 @@ void WindowEventDispatcher::OnOtherRootGotCapture() {
   }
 #endif
 
-  mouse_moved_handler_ = NULL;
-  mouse_pressed_handler_ = NULL;
+  mouse_moved_handler_ = nullptr;
+  mouse_pressed_handler_ = nullptr;
 }
 
 void WindowEventDispatcher::SetNativeCapture() {
@@ -559,7 +559,7 @@ ui::EventDispatchDetails WindowEventDispatcher::PostDispatchEvent(
   if (!target || target != event_dispatch_target_)
     details.target_destroyed = true;
   event_dispatch_target_ = old_dispatch_target_;
-  old_dispatch_target_ = NULL;
+  old_dispatch_target_ = nullptr;
 #ifndef NDEBUG
   DCHECK(!event_dispatch_target_ || window()->Contains(event_dispatch_target_));
 #endif
@@ -921,7 +921,7 @@ DispatchDetails WindowEventDispatcher::PreDispatchMouseEvent(
           event->SetHandled();
           return details;
         }
-        mouse_moved_handler_ = NULL;
+        mouse_moved_handler_ = nullptr;
       }
       break;
     case ui::ET_MOUSE_MOVED:
@@ -950,7 +950,7 @@ DispatchDetails WindowEventDispatcher::PreDispatchMouseEvent(
           return target_details;
         }
         if (details.target_destroyed || target_details.target_destroyed) {
-          mouse_moved_handler_ = NULL;
+          mouse_moved_handler_ = nullptr;
           event->SetHandled();
           return target_details;
         }
@@ -974,7 +974,7 @@ DispatchDetails WindowEventDispatcher::PreDispatchMouseEvent(
         mouse_pressed_handler_ = target;
       break;
     case ui::ET_MOUSE_RELEASED:
-      mouse_pressed_handler_ = NULL;
+      mouse_pressed_handler_ = nullptr;
       break;
     default:
       break;

ui/compositor/layer_animator.cc

@@ -32,9 +32,8 @@
         ? function(running_anim.sequence()) \
         : false)
 #define SAFE_INVOKE_PTR(function, running_anim)                           \
-    ((running_anim.is_sequence_alive()) \
-        ? function(running_anim.sequence()) \
-        : NULL)
+  ((running_anim.is_sequence_alive()) ? function(running_anim.sequence()) \
+                                      : nullptr)
 
 namespace ui {
 
@@ -66,7 +65,7 @@ LayerAnimator::~LayerAnimator() {
       running_animations_[i].sequence()->OnAnimatorDestroyed();
   }
   ClearAnimationsInternal();
-  delegate_ = NULL;
+  delegate_ = nullptr;
   DCHECK(!animation_->animation_timeline());
 }
 
@@ -660,7 +659,7 @@ LayerAnimator::RunningAnimation* LayerAnimator::GetRunningAnimation(
     if ((*iter).sequence()->properties() & property)
       return &(*iter);
   }
-  return NULL;
+  return nullptr;
 }
 
 void LayerAnimator::AddToQueueIfNotPresent(LayerAnimationSequence* animation) {
@@ -735,7 +734,7 @@ void LayerAnimator::ImmediatelySetNewTarget(LayerAnimationSequence* sequence) {
     return;
 
   LayerAnimationSequence* removed = RemoveAnimation(sequence);
-  DCHECK(removed == NULL || removed == sequence);
+  DCHECK(removed == nullptr || removed == sequence);
   if (!weak_sequence_ptr.get())
     return;
 
@@ -950,7 +949,7 @@ void LayerAnimator::PurgeDeletedAnimations() {
 }
 
 LayerAnimatorCollection* LayerAnimator::GetLayerAnimatorCollection() {
-  return delegate_ ? delegate_->GetLayerAnimatorCollection() : NULL;
+  return delegate_ ? delegate_->GetLayerAnimatorCollection() : nullptr;
 }
 
 void LayerAnimator::NotifyAnimationStarted(base::TimeTicks monotonic_time,

ui/events/gesture_detection/gesture_detector.h

@@ -100,7 +100,7 @@ class GESTURE_DETECTION_EXPORT GestureDetector {
   // Note: The listener must never be changed while |is_double_tapping| is true.
   void SetDoubleTapListener(DoubleTapListener* double_tap_listener);
 
-  bool has_doubletap_listener() const { return double_tap_listener_ != NULL; }
+  bool has_doubletap_listener() const { return !!double_tap_listener_; }
 
   bool is_double_tapping() const { return is_double_tapping_; }