Do not hide shadow underlay for max/fullscreen state even if the client disables the shadow.

During the state transition, ARC preserves windows being deleted,
however the main window is deleted (thus, window frame is empty) which disables the shadow.

BUG=711514
TEST=covered by unit tests.
 manual. Instal & start "Clash Royal", then F4 to toggle fullscreen.

Review-Url: https://codereview.chromium.org/2820493004
Cr-Commit-Position: refs/heads/master@{#464819}
(cherry picked from commit ae72f92)

Review-Url: https://codereview.chromium.org/2821963002 .
Cr-Commit-Position: refs/branch-heads/3071@{#52}
Cr-Branched-From: a106f0a-refs/heads/master@{#464641}

Author: mitoshima

components/exo/shell_surface.cc

@@ -1558,7 +1558,15 @@ void ShellSurface::UpdateShadow() {
   if (!widget_ || !surface_)
     return;
   aura::Window* window = widget_->GetNativeWindow();
-  if (!shadow_enabled_) {
+
+  bool underlay_capture_events =
+      WMHelper::GetInstance()->IsSpokenFeedbackEnabled() && widget_->IsActive();
+  bool black_background_enabled =
+      ((widget_->IsFullscreen() || widget_->IsMaximized()) ||
+       underlay_capture_events) &&
+      ash::wm::GetWindowState(window)->allow_set_bounds_direct() &&
+      window->layer()->GetTargetTransform().IsIdentity();
+  if (!shadow_enabled_ && !black_background_enabled) {
     wm::SetShadowElevation(window, wm::ShadowElevation::NONE);
     if (shadow_underlay_)
       shadow_underlay_->Hide();
@@ -1626,10 +1634,6 @@ void ShellSurface::UpdateShadow() {
       }
     }
 
-    bool underlay_capture_events =
-        WMHelper::GetInstance()->IsSpokenFeedbackEnabled() &&
-        widget_->IsActive();
-
     float shadow_underlay_opacity = shadow_background_opacity_;
 
     // Put the black background layer behind the window if
@@ -1639,10 +1643,7 @@ void ShellSurface::UpdateShadow() {
     //    thus the background can be visible).
     // 3) the window has no transform (the transformed background may
     //    not cover the entire background, e.g. overview mode).
-    if ((widget_->IsFullscreen() || widget_->IsMaximized() ||
-         underlay_capture_events) &&
-        ash::wm::GetWindowState(window)->allow_set_bounds_direct() &&
-        window->layer()->GetTargetTransform().IsIdentity()) {
+    if (black_background_enabled) {
       if (shadow_underlay_in_surface_) {
         shadow_underlay_bounds = gfx::Rect(surface_->window()->bounds().size());
       } else {
@@ -1657,22 +1658,21 @@ void ShellSurface::UpdateShadow() {
     if (!shadow_underlay_in_surface_)
       shadow_underlay_bounds = shadow_bounds;
 
+    shadow_underlay_->SetBounds(shadow_underlay_bounds);
+
     // Constrain the underlay bounds to the client area in case shell surface
     // frame is enabled.
     if (frame_enabled_) {
       shadow_underlay_bounds.Intersect(
           widget_->non_client_view()->frame_view()->GetBoundsForClientView());
     }
 
-    shadow_underlay_->SetBounds(shadow_underlay_bounds);
-
     // TODO(oshima): Setting to the same value should be no-op.
     // crbug.com/642223.
     if (shadow_underlay_opacity !=
         shadow_underlay_->layer()->GetTargetOpacity()) {
       shadow_underlay_->layer()->SetOpacity(shadow_underlay_opacity);
     }
-
     shadow_underlay_->Show();
 
     wm::Shadow* shadow = wm::ShadowController::GetShadowForWindow(window);

components/exo/shell_surface_unittest.cc

@@ -832,6 +832,20 @@ TEST_F(ShellSurfaceTest, ShadowStartMaximized) {
   ASSERT_TRUE(shell_surface->shadow_underlay());
   EXPECT_TRUE(shell_surface->shadow_underlay()->IsVisible());
 
+  shell_surface->SetRectangularSurfaceShadow(gfx::Rect(0, 0, 0, 0));
+  // Underlay should be created even without shadow.
+  ASSERT_TRUE(shell_surface->shadow_underlay());
+  EXPECT_TRUE(shell_surface->shadow_underlay()->IsVisible());
+  shell_surface->SetRectangularShadowEnabled(false);
+  surface->Commit();
+  // Underlay should be created even without shadow.
+  ASSERT_TRUE(shell_surface->shadow_underlay());
+  EXPECT_TRUE(shell_surface->shadow_underlay()->IsVisible());
+
+  shell_surface->SetRectangularShadowEnabled(true);
+  shell_surface->SetRectangularSurfaceShadow(gfx::Rect(10, 10, 100, 100));
+  surface->Commit();
+
   // Restore the window and make sure the shadow is created, visible and
   // has the latest bounds.
   widget->Restore();