Android: Constant alpha on gesture navigation sheet scrim

This CL removes |onSheetStateChanged| that updates scrim alpha
to the height of the sheet view. Scrim alpha in opened state
stays constant.

Bug: 993032
Change-Id: Idabf5735e282bbd28e4e290a67ce033c5a9c8f08
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1760834
Commit-Queue: Jinsuk Kim <jinsukkim@chromium.org>
Reviewed-by: Theresa  <twellington@chromium.org>
Reviewed-by: Matthew Jones <mdjones@chromium.org>
Cr-Commit-Position: refs/heads/master@{#691962}

chrome/android/java/src/org/chromium/chrome/browser/widget/ScrimView.java

@@ -137,7 +137,7 @@ public class ScrimView extends View implements View.OnClickListener {
     }
 
     /** The duration for the fading animation. */
-    private static final int FADE_DURATION_MS = 250;
+    private static final int FADE_DURATION_MS = 300;
 
     /** A means of changing the statusbar color. */
     private final StatusBarScrimDelegate mStatusBarScrimDelegate;

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

@@ -5,7 +5,6 @@
 package org.chromium.chrome.browser.widget.bottomsheet;
 
 import android.app.Activity;
-import android.view.View;
 
 import org.chromium.chrome.R;
 import org.chromium.chrome.browser.ActivityTabProvider;
@@ -192,7 +191,7 @@ public class BottomSheetController implements Destroyable {
                     return;
                 }
 
-                scrim.hideScrim(false);
+                scrim.hideScrim(true);
 
                 // If the sheet is closed, it is an opportunity for another content to try to take
                 // its place if it is a higher priority.
@@ -212,19 +211,6 @@ public class BottomSheetController implements Destroyable {
                 showNextContent(true);
             }
 
-            @Override
-            public void onTransitionPeekToHalf(float transitionFraction) {
-                if (mBottomSheet.getCurrentSheetContent() != null
-                        && mBottomSheet.getCurrentSheetContent().hasCustomScrimLifecycle()) {
-                    return;
-                }
-
-                // TODO(mdjones): This event should not occur after the bottom sheet is closed.
-                if (scrim.getVisibility() == View.VISIBLE) {
-                    scrim.setViewAlpha(transitionFraction);
-                }
-            }
-
             @Override
             public void onSheetOffsetChanged(float heightFraction, float offsetPx) {
                 mSnackbarManager.dismissAllSnackbars();

chrome/android/javatests/src/org/chromium/chrome/browser/widget/ScrimTest.java

@@ -117,6 +117,7 @@ public class ScrimTest {
     @SmallTest
     @Feature({"Scrim"})
     public void testBottomSheetScrim() throws InterruptedException, TimeoutException {
+        mScrim.disableAnimationForTesting(true);
         assertScrimVisibility(false);
         assertFalse("Nothing should be obscuring the tab.",
                 mActivityTestRule.getActivity().isViewObscuringAllTabs());
@@ -131,7 +132,7 @@ public class ScrimTest {
         assertScrimVisibility(true);
         assertTrue("A view should be obscuring the tab.",
                 mActivityTestRule.getActivity().isViewObscuringAllTabs());
-        assertEquals("The scrim alpha should be 1.", 1f, mScrim.getAlpha(), MathUtils.EPSILON);
+        assertEquals("The scrim alpha should be 0.", 0f, mScrim.getAlpha(), MathUtils.EPSILON);
 
         ThreadUtils.runOnUiThreadBlocking(
                 () -> mBottomSheet.setSheetState(BottomSheet.SheetState.PEEK, false));