[VK] Fix work area bug in shelf layout manager.

In a previous CL [1], we made changes to the shelf layout manager to
use occluded and displaced bounds. However, we introduced a bug where
the work area would not reset when we hide the accessibility keyboard,
leaving a large gap in the screen.

The code now makes more sense: we should be changing the work area
whenever the displaced bounds change.

We add a test for this. We also removed some calls to |LayoutShelf| in
existing tests; |LayoutShelf| doesn't get called in real situations.
Calling |LayoutShelf| manually will always change the work area,
which is not what happens in practice.

[1] https://chromium-review.googlesource.com/c/chromium/src/+/1146530

TBR=jamescook@chromium.org

Bug: 870503
Change-Id: I80a6aa90f1bce8e59e6c7cde2e3f181c31fc6907
Reviewed-on: https://chromium-review.googlesource.com/1160827Reviewed-by: Darren Shen <shend@chromium.org>
Commit-Queue: Darren Shen <shend@chromium.org>
Cr-Commit-Position: refs/heads/master@{#580394}

ash/shelf/shelf_layout_manager.cc

@@ -496,11 +496,12 @@ void ShelfLayoutManager::OnWindowActivated(ActivationReason reason,
 
 void ShelfLayoutManager::OnKeyboardAppearanceChanged(
     const keyboard::KeyboardStateDescriptor& state) {
+  // If displaced bounds changed, then change the work area too.
+  bool change_work_area = state.displaced_bounds != keyboard_displaced_bounds_;
+
   keyboard_occluded_bounds_ = state.occluded_bounds;
   keyboard_displaced_bounds_ = state.displaced_bounds;
 
-  // If there are displaced bounds, then change the work area.
-  bool change_work_area = !keyboard_displaced_bounds_.IsEmpty();
   LayoutShelfAndUpdateBounds(change_work_area);
 }
 

ash/shelf/shelf_layout_manager_unittest.cc

@@ -2181,7 +2181,6 @@ TEST_F(ShelfLayoutManagerKeyboardTest, ShelfNotMoveOnKeyboardOpen) {
   // Open keyboard in non-sticky mode.
   kb_controller->ShowKeyboard(false);
   NotifyKeyboardChanging(layout_manager, false, keyboard_bounds());
-  layout_manager->LayoutShelf();
 
   // Shelf position should not be changed.
   EXPECT_EQ(orig_bounds, GetShelfWidget()->GetWindowBoundsInScreen());
@@ -2200,7 +2199,6 @@ TEST_F(ShelfLayoutManagerKeyboardTest,
   // Open keyboard in non-sticky mode.
   kb_controller->ShowKeyboard(false);
   NotifyKeyboardChanging(layout_manager, false, keyboard_bounds());
-  layout_manager->LayoutShelf();
 
   // Work area should not be changed.
   EXPECT_EQ(orig_work_area,
@@ -2208,7 +2206,6 @@ TEST_F(ShelfLayoutManagerKeyboardTest,
 
   kb_controller->HideKeyboardExplicitlyBySystem();
   NotifyKeyboardChanging(layout_manager, false, gfx::Rect());
-  layout_manager->LayoutShelf();
   EXPECT_EQ(orig_work_area,
             display::Screen::GetScreen()->GetPrimaryDisplay().work_area());
 }
@@ -2224,11 +2221,18 @@ TEST_F(ShelfLayoutManagerKeyboardTest, ShelfShouldChangeWorkAreaInStickyMode) {
   // Open keyboard in sticky mode.
   kb_controller->ShowKeyboard(true);
   NotifyKeyboardChanging(layout_manager, true, keyboard_bounds());
-  layout_manager->LayoutShelf();
 
   // Work area should be changed.
   EXPECT_NE(orig_work_area,
             display::Screen::GetScreen()->GetPrimaryDisplay().work_area());
+
+  // Hide the keyboard.
+  kb_controller->HideKeyboardByUser();
+  NotifyKeyboardChanging(layout_manager, true, gfx::Rect());
+
+  // Work area should be reset to its original value.
+  EXPECT_EQ(orig_work_area,
+            display::Screen::GetScreen()->GetPrimaryDisplay().work_area());
 }
 
 }  // namespace ash