Dismiss content in bottom sheet when closed

This only applies if the content does not have a custom lifecycle.
This patch also adds a test for this functionality.

Change-Id: Ia5f2d87e3d3d0b8d83b7181e23e3b403fbd8b0d7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1624813
Commit-Queue: Matthew Jones <mdjones@chromium.org>
Reviewed-by: Theresa <twellington@chromium.org>
Cr-Commit-Position: refs/heads/master@{#662891}

chrome/android/java/src/org/chromium/chrome/browser/widget/bottomsheet/BottomSheetController.java

@@ -201,6 +201,10 @@ public class BottomSheetController implements Destroyable {
                 }
 
                 scrim.hideScrim(false);
+
+                // If not using a custom lifecycle, notify the controller that the sheet's content
+                // has been dismissed.
+                hideContent(mBottomSheet.getCurrentSheetContent(), false);
             }
 
             @Override

chrome/android/javatests/src/org/chromium/chrome/browser/widget/bottomsheet/BottomSheetControllerTest.java

@@ -255,6 +255,29 @@ public class BottomSheetControllerTest {
         assertEquals(customLifecycleContent, mBottomSheet.getCurrentSheetContent());
     }
 
+    @Test
+    @MediumTest
+    public void testCloseEvent() throws TimeoutException, InterruptedException {
+        requestContentInSheet(mHighPriorityContent, true);
+        expandSheet();
+
+        CallbackHelper contentChangedHelper = new CallbackHelper();
+        mBottomSheet.addObserver(new EmptyBottomSheetObserver() {
+            @Override
+            public void onSheetContentChanged(BottomSheetContent content) {
+                contentChangedHelper.notifyCalled();
+            }
+        });
+
+        ThreadUtils.runOnUiThreadBlocking(
+                () -> mBottomSheet.setSheetState(BottomSheet.SheetState.HIDDEN, false));
+
+        contentChangedHelper.waitForCallback(0, 1);
+
+        assertEquals("The sheet's content should be null!", null,
+                mSheetController.getBottomSheet().getCurrentSheetContent());
+    }
+
     /**
      * Request content be shown in the bottom sheet and end animations.
      * @param content The content to show.