Revert "views: removal of dead code in NativeViewHost"

This reverts commit 0ee09a04.

Reason for revert: Regresses Assistant UI.

Original change's description:
> views: removal of dead code in NativeViewHost
>
> NativeViewHost has code to deal with being clipped by an ancestor. This logic
> dates back to when we used NativeViewHost more often, and in particular when
> NativeViewHost was contained in a ScrollView. AFAIK we no longer have this
> scenario, so, this removes the unnecessary logic.
>
> BUG=none
> TEST=covered by tests
>
> Change-Id: I7b1a9ba047bd7c4abab68f9fe49c651bf50209d2
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1560130
> Commit-Queue: Scott Violet <sky@chromium.org>
> Reviewed-by: Michael Wasserman <msw@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#649355}

TBR=sky@chromium.org,msw@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: b:130305523
Change-Id: Ib0b5dba24bb4e376f3cdad11d19d59e318fd1b2e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1563031Reviewed-by: Scott Violet <sky@chromium.org>
Commit-Queue: David Black <dmblack@google.com>
Cr-Commit-Position: refs/heads/master@{#649775}

ui/views/controls/native/native_view_host.cc

@@ -97,7 +97,24 @@ void NativeViewHost::Layout() {
   if (!native_view_ || !native_wrapper_.get())
     return;
 
-  if (IsDrawn() && !bounds().IsEmpty()) {
+  gfx::Rect vis_bounds = GetVisibleBounds();
+  bool visible = !vis_bounds.IsEmpty();
+
+  if (visible && !fast_resize_) {
+    if (vis_bounds.size() != size()) {
+      // Only a portion of the Widget is really visible.
+      int x = vis_bounds.x();
+      int y = vis_bounds.y();
+      native_wrapper_->InstallClip(x, y, vis_bounds.width(),
+                                   vis_bounds.height());
+    } else if (native_wrapper_->HasInstalledClip()) {
+      // The whole widget is visible but we installed a clip on the widget,
+      // uninstall it.
+      native_wrapper_->UninstallClip();
+    }
+  }
+
+  if (visible) {
     // Since widgets know nothing about the View hierarchy (they are direct
     // children of the Widget that hosts our View hierarchy) they need to be
     // positioned in the coordinate system of the Widget, not the current
@@ -113,6 +130,7 @@ void NativeViewHost::Layout() {
   } else {
     native_wrapper_->HideWidget();
   }
+  fast_resize_at_last_layout_ = visible && fast_resize_;
 }
 
 void NativeViewHost::OnPaint(gfx::Canvas* canvas) {

ui/views/controls/native/native_view_host.h

@@ -86,6 +86,11 @@ class VIEWS_EXPORT NativeViewHost : public View {
   void set_fast_resize(bool fast_resize) { fast_resize_ = fast_resize; }
   bool fast_resize() const { return fast_resize_; }
 
+  // Value of fast_resize() the last time Layout() was invoked.
+  bool fast_resize_at_last_layout() const {
+    return fast_resize_at_last_layout_;
+  }
+
   gfx::NativeView native_view() const { return native_view_; }
 
   void NativeViewDestroyed();
@@ -133,6 +138,9 @@ class VIEWS_EXPORT NativeViewHost : public View {
   // in the setter/accessor above.
   bool fast_resize_ = false;
 
+  // Value of |fast_resize_| during the last call to Layout.
+  bool fast_resize_at_last_layout_ = false;
+
   DISALLOW_COPY_AND_ASSIGN(NativeViewHost);
 };
 

ui/views/controls/native/native_view_host_aura.cc

@@ -183,12 +183,21 @@ void NativeViewHostAura::SetHitTestTopInset(int top_inset) {
   UpdateInsets();
 }
 
+void NativeViewHostAura::InstallClip(int x, int y, int w, int h) {
+  clip_rect_ = std::make_unique<gfx::Rect>(
+      host_->ConvertRectToWidget(gfx::Rect(x, y, w, h)));
+}
+
 int NativeViewHostAura::GetHitTestTopInset() const {
   return top_inset_;
 }
 
 bool NativeViewHostAura::HasInstalledClip() {
-  return clip_rect_.has_value();
+  return !!clip_rect_;
+}
+
+void NativeViewHostAura::UninstallClip() {
+  clip_rect_.reset();
 }
 
 void NativeViewHostAura::ShowWidget(int x,
@@ -198,11 +207,12 @@ void NativeViewHostAura::ShowWidget(int x,
                                     int native_w,
                                     int native_h) {
   if (host_->fast_resize()) {
-    clip_rect_ = gfx::Rect(x, y, w, h);
+    gfx::Point origin(x, y);
+    views::View::ConvertPointFromWidget(host_, &origin);
+    InstallClip(origin.x(), origin.y(), w, h);
     native_w = host_->native_view()->bounds().width();
     native_h = host_->native_view()->bounds().height();
   } else {
-    clip_rect_.reset();
     gfx::Transform transform = original_transform_;
     if (w > 0 && h > 0 && native_w > 0 && native_h > 0) {
       transform.Scale(static_cast<SkMScalar>(w) / native_w,
@@ -215,7 +225,7 @@ void NativeViewHostAura::ShowWidget(int x,
     }
   }
 
-  clipping_window_->SetBounds(clip_rect_.value_or(gfx::Rect(x, y, w, h)));
+  clipping_window_->SetBounds(clip_rect_ ? *clip_rect_ : gfx::Rect(x, y, w, h));
   gfx::Point clip_offset = clipping_window_->bounds().origin();
   host_->native_view()->SetBounds(
       gfx::Rect(x - clip_offset.x(), y - clip_offset.y(), native_w, native_h));
@@ -224,7 +234,6 @@ void NativeViewHostAura::ShowWidget(int x,
 }
 
 void NativeViewHostAura::HideWidget() {
-  clip_rect_.reset();
   host_->native_view()->Hide();
   clipping_window_->Hide();
 }

ui/views/controls/native/native_view_host_aura.h

@@ -7,7 +7,6 @@
 
 #include "base/compiler_specific.h"
 #include "base/macros.h"
-#include "base/optional.h"
 #include "ui/aura/window_observer.h"
 #include "ui/compositor/layer_owner.h"
 #include "ui/gfx/transform.h"
@@ -37,7 +36,9 @@ class NativeViewHostAura : public NativeViewHostWrapper,
   bool SetCustomMask(std::unique_ptr<ui::LayerOwner> mask) override;
   void SetHitTestTopInset(int top_inset) override;
   int GetHitTestTopInset() const override;
+  void InstallClip(int x, int y, int w, int h) override;
   bool HasInstalledClip() override;
+  void UninstallClip() override;
   void ShowWidget(int x, int y, int w, int h, int native_w, int native_h)
       override;
   void HideWidget() override;
@@ -88,7 +89,7 @@ class NativeViewHostAura : public NativeViewHostWrapper,
   // clipping to occur. This is positioned in the coordinate space of
   // host_->GetWidget().
   std::unique_ptr<aura::Window> clipping_window_;
-  base::Optional<gfx::Rect> clip_rect_;
+  std::unique_ptr<gfx::Rect> clip_rect_;
 
   // This mask exists for the sake of SetCornerRadius().
   std::unique_ptr<ui::LayerOwner> mask_;

ui/views/controls/native/native_view_host_aura_unittest.cc

@@ -278,6 +278,48 @@ TEST_F(NativeViewHostAuraTest, BoundsWhileScaling) {
   DestroyHost();
 }
 
+// Test installing and uninstalling a clip.
+TEST_F(NativeViewHostAuraTest, InstallClip) {
+  CreateHost();
+  toplevel()->SetBounds(gfx::Rect(20, 20, 100, 100));
+
+  // Without a clip, the clipping window should always be positioned at the
+  // requested coordinates with the native view positioned at the origin of the
+  // clipping window.
+  native_host()->ShowWidget(10, 20, 100, 100, 100, 100);
+  EXPECT_EQ(gfx::Rect(0, 0, 100, 100).ToString(),
+            host()->native_view()->bounds().ToString());
+  EXPECT_EQ(gfx::Rect(10, 20, 100, 100).ToString(),
+            clipping_window()->bounds().ToString());
+
+  // Clip to the bottom right quarter of the native view.
+  native_host()->InstallClip(60, 70, 50, 50);
+  native_host()->ShowWidget(10, 20, 100, 100, 100, 100);
+  EXPECT_EQ(gfx::Rect(-50, -50, 100, 100).ToString(),
+            host()->native_view()->bounds().ToString());
+  EXPECT_EQ(gfx::Rect(60, 70, 50, 50).ToString(),
+            clipping_window()->bounds().ToString());
+
+  // Clip to the center of the native view.
+  native_host()->InstallClip(35, 45, 50, 50);
+  native_host()->ShowWidget(10, 20, 100, 100, 100, 100);
+  EXPECT_EQ(gfx::Rect(-25, -25, 100, 100).ToString(),
+            host()->native_view()->bounds().ToString());
+  EXPECT_EQ(gfx::Rect(35, 45, 50, 50).ToString(),
+            clipping_window()->bounds().ToString());
+
+  // Uninstalling the clip should make the clipping window match the native view
+  // again.
+  native_host()->UninstallClip();
+  native_host()->ShowWidget(10, 20, 100, 100, 100, 100);
+  EXPECT_EQ(gfx::Rect(0, 0, 100, 100).ToString(),
+            host()->native_view()->bounds().ToString());
+  EXPECT_EQ(gfx::Rect(10, 20, 100, 100).ToString(),
+            clipping_window()->bounds().ToString());
+
+  DestroyHost();
+}
+
 // Ensure native view is parented to the root window after detaching. This is
 // a regression test for http://crbug.com/389261.
 TEST_F(NativeViewHostAuraTest, ParentAfterDetach) {

ui/views/controls/native/native_view_host_mac.h

@@ -42,7 +42,9 @@ class NativeViewHostMac : public NativeViewHostWrapper,
   bool SetCustomMask(std::unique_ptr<ui::LayerOwner> mask) override;
   void SetHitTestTopInset(int top_inset) override;
   int GetHitTestTopInset() const override;
+  void InstallClip(int x, int y, int w, int h) override;
   bool HasInstalledClip() override;
+  void UninstallClip() override;
   void ShowWidget(int x, int y, int w, int h, int native_w, int native_h)
       override;
   void HideWidget() override;

ui/views/controls/native/native_view_host_mac.mm

@@ -169,10 +169,18 @@ int NativeViewHostMac::GetHitTestTopInset() const {
   return 0;
 }
 
+void NativeViewHostMac::InstallClip(int x, int y, int w, int h) {
+  NOTIMPLEMENTED();
+}
+
 bool NativeViewHostMac::HasInstalledClip() {
   return false;
 }
 
+void NativeViewHostMac::UninstallClip() {
+  NOTIMPLEMENTED();
+}
+
 void NativeViewHostMac::ShowWidget(int x,
                                    int y,
                                    int w,

ui/views/controls/native/native_view_host_wrapper.h

@@ -51,10 +51,20 @@ class NativeViewHostWrapper {
   virtual void SetHitTestTopInset(int top_inset) = 0;
   virtual int GetHitTestTopInset() const = 0;
 
+  // Installs a clip on the gfx::NativeView. These values are in the coordinate
+  // space of the Widget, so if this method is called from ShowWidget
+  // then the values need to be translated.
+  virtual void InstallClip(int x, int y, int w, int h) = 0;
+
   // Whether or not a clip has been installed on the wrapped gfx::NativeView.
-  // A clip is only installed during fast-resize.
   virtual bool HasInstalledClip() = 0;
 
+  // Removes the clip installed on the gfx::NativeView by way of InstallClip. A
+  // following call to ShowWidget should occur after calling this method to
+  // position the gfx::NativeView correctly, since the clipping process may have
+  // adjusted its position.
+  virtual void UninstallClip() = 0;
+
   // Shows the gfx::NativeView within the specified region (relative to the
   // parent native view) and with the given native size. The content will
   // appear scaled if the |native_w| or |native_h| are different from |w| or