[WebLayer] Save browser controls UI state between BrowserFragment restarts

This CL makes BrowserImpl save the UI state of BrowserViewController
when destroying/creating it so we can save the controls location. It
doesn't use onStoreInstanceState directly because the
BrowserControlsContainerView lifecycle doesn't exactly match what
Android expects (onStoreInstanceState gets called after BCCV is already
destroyed).

Bug: 1120209
Change-Id: Ibedf4f8ad1e01f29518b404d94961b0e97689b9c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2368479Reviewed-by: Bo <boliu@chromium.org>
Commit-Queue: Robbie McElrath <rmcelrath@chromium.org>
Cr-Commit-Position: refs/heads/master@{#801158}

weblayer/browser/java/org/chromium/weblayer_private/BrowserControlsContainerView.java

@@ -11,6 +11,8 @@ import android.view.View;
 import android.view.ViewParent;
 import android.widget.FrameLayout;
 
+import androidx.annotation.Nullable;
+
 import org.chromium.base.MathUtils;
 import org.chromium.base.annotations.CalledByNative;
 import org.chromium.base.annotations.JNINamespace;
@@ -59,9 +61,25 @@ class BrowserControlsContainerView extends FrameLayout {
 
     private static final long SYSTEM_UI_VIEWPORT_UPDATE_DELAY_MS = 500;
 
+    /** Stores the state needed to reconstruct offsets after recreating this class. */
+    /* package */ static class State {
+        private final int mControlsOffset;
+        private final int mContentOffset;
+
+        private State(int controlsOffset, int contentOffset) {
+            mControlsOffset = controlsOffset;
+            mContentOffset = contentOffset;
+        }
+    }
+
     private final Delegate mDelegate;
     private final boolean mIsTop;
 
+    // The state returned by a previous BrowserControlsContainerView instance's getState() method.
+    // This is saved rather than directly applied because layout needs to occur before we can apply
+    // the offsets.
+    private State mSavedState;
+
     private long mNativeBrowserControlsContainerView;
 
     private ViewResourceAdapter mViewResourceAdapter;
@@ -132,10 +150,11 @@ class BrowserControlsContainerView extends FrameLayout {
     }
 
     BrowserControlsContainerView(Context context, ContentViewRenderView contentViewRenderView,
-            Delegate delegate, boolean isTop) {
+            Delegate delegate, boolean isTop, @Nullable State savedState) {
         super(context);
         mDelegate = delegate;
         mIsTop = isTop;
+        mSavedState = savedState;
         mContentViewRenderView = contentViewRenderView;
         mNativeBrowserControlsContainerView =
                 BrowserControlsContainerViewJni.get().createBrowserControlsContainerView(
@@ -333,9 +352,21 @@ class BrowserControlsContainerView extends FrameLayout {
             createAdapterAndLayer();
             if (prevHeight == 0) {
                 assert heightChanged;
-                // If there wasn't a View before (or it had 0 height), move the new View off the
-                // screen until we know where to position it.
-                moveControlsOffScreen();
+                // If there wasn't a View before and we have non-empty saved state from a previous
+                // BrowserControlsContainerView instance, apply those saved offsets now. We can't
+                // rely on BrowserControlsOffsetManager to notify us of the correct location as we
+                // usually do because it only notifies us when offsets change, but it likely didn't
+                // get destroyed when the BrowserFragment got recreated, so it won't notify us
+                // because it thinks we already have the correct offsets.
+                if (mSavedState != null) {
+                    onOffsetsChanged(mSavedState.mControlsOffset, mSavedState.mContentOffset);
+                } else {
+                    // If there wasn't a View before (or it had 0 height) and there's no state from
+                    // a previous instance of this class, move the new View off the screen until
+                    // BrowserControlsOffsetManager tells us where to position it.
+                    moveControlsOffScreen();
+                }
+                mSavedState = null;
             }
         } else if (mViewResourceAdapter != null) {
             BrowserControlsContainerViewJni.get().setControlsSize(
@@ -352,6 +383,10 @@ class BrowserControlsContainerView extends FrameLayout {
         cancelDelayedFullscreenRunnable();
     }
 
+    /* package */ State getState() {
+        return new State(mControlsOffset, mContentOffset);
+    }
+
     private void cancelDelayedFullscreenRunnable() {
         if (mSystemUiFullscreenResizeRunnable == null) return;
         removeCallbacks(mSystemUiFullscreenResizeRunnable);

weblayer/browser/java/org/chromium/weblayer_private/BrowserImpl.java

@@ -56,6 +56,10 @@ public class BrowserImpl extends IBrowser.Stub implements View.OnAttachStateChan
     private final ProfileImpl mProfile;
     private Context mEmbedderActivityContext;
     private BrowserViewController mViewController;
+    // Used to save UI state between destroyAttachmentState() and createAttachmentState() calls so
+    // it can be preserved during device rotations or other events that cause the Fragment to be
+    // recreated.
+    private BrowserViewController.State mViewControllerState;
     private FragmentWindowAndroid mWindowAndroid;
     private IBrowserClient mClient;
     private LocaleChangedBroadcastReceiver mLocaleReceiver;
@@ -136,7 +140,7 @@ public class BrowserImpl extends IBrowser.Stub implements View.OnAttachStateChan
         assert mEmbedderActivityContext == null;
         mWindowAndroid = windowAndroid;
         mEmbedderActivityContext = embedderAppContext;
-        mViewController = new BrowserViewController(windowAndroid, this);
+        mViewController = new BrowserViewController(windowAndroid, this, mViewControllerState);
         mLocaleReceiver = new LocaleChangedBroadcastReceiver(windowAndroid.getContext().get());
         mPasswordEchoEnabled = null;
     }
@@ -533,6 +537,7 @@ public class BrowserImpl extends IBrowser.Stub implements View.OnAttachStateChan
             mLocaleReceiver = null;
         }
         if (mViewController != null) {
+            mViewControllerState = mViewController.getState();
             mViewController.destroy();
             mViewController = null;
             mViewAttachedToWindow = false;

weblayer/browser/java/org/chromium/weblayer_private/BrowserViewController.java

@@ -15,6 +15,8 @@ import android.webkit.ValueCallback;
 import android.widget.FrameLayout;
 import android.widget.RelativeLayout;
 
+import androidx.annotation.Nullable;
+
 import org.chromium.base.annotations.JNINamespace;
 import org.chromium.components.browser_ui.modaldialog.AppModalPresenter;
 import org.chromium.components.browser_ui.widget.InsetObserverView;
@@ -36,6 +38,18 @@ public final class BrowserViewController
         implements BrowserControlsContainerView.Delegate,
                    WebContentsGestureStateTracker.OnGestureStateChangedListener,
                    ModalDialogManager.ModalDialogManagerObserver {
+    /** Information needed to restore the UI state after recreating the BrowserViewController. */
+    /* package */ static class State {
+        private BrowserControlsContainerView.State mTopControlsState;
+        private BrowserControlsContainerView.State mBottomControlsState;
+
+        private State(BrowserControlsContainerView.State topControlsState,
+                BrowserControlsContainerView.State bottomControlsState) {
+            mTopControlsState = topControlsState;
+            mBottomControlsState = bottomControlsState;
+        }
+    }
+
     private final ContentViewRenderView mContentViewRenderView;
     // Child of mContentViewRenderView. Be very careful adding Views to this, as any Views are not
     // accessible (ContentView provides it's own accessible implementation that interacts with
@@ -72,8 +86,8 @@ public final class BrowserViewController
      */
     private boolean mCachedDoBrowserControlsShrinkRendererSize;
 
-    public BrowserViewController(
-            FragmentWindowAndroid windowAndroid, View.OnAttachStateChangeListener listener) {
+    public BrowserViewController(FragmentWindowAndroid windowAndroid,
+            View.OnAttachStateChangeListener listener, @Nullable State savedState) {
         mWindowAndroid = windowAndroid;
         mOnAttachedStateChangeListener = listener;
         Context context = mWindowAndroid.getContext().get();
@@ -83,10 +97,12 @@ public final class BrowserViewController
         mContentViewRenderView.onNativeLibraryLoaded(
                 mWindowAndroid, ContentViewRenderView.MODE_SURFACE_VIEW);
         mTopControlsContainerView =
-                new BrowserControlsContainerView(context, mContentViewRenderView, this, true);
+                new BrowserControlsContainerView(context, mContentViewRenderView, this, true,
+                        (savedState == null) ? null : savedState.mTopControlsState);
         mTopControlsContainerView.setId(View.generateViewId());
         mBottomControlsContainerView =
-                new BrowserControlsContainerView(context, mContentViewRenderView, this, false);
+                new BrowserControlsContainerView(context, mContentViewRenderView, this, false,
+                        (savedState == null) ? null : savedState.mBottomControlsState);
         mBottomControlsContainerView.setId(View.generateViewId());
         mContentView = ContentView.createContentView(
                 context, mTopControlsContainerView.getEventOffsetHandler(), null /* webContents */);
@@ -275,6 +291,11 @@ public final class BrowserViewController
         onDialogVisibilityChanged(false);
     }
 
+    /* package */ State getState() {
+        return new State(
+                mTopControlsContainerView.getState(), mBottomControlsContainerView.getState());
+    }
+
     private void onDialogVisibilityChanged(boolean showing) {
         if (WebLayerFactoryImpl.getClientMajorVersion() < 82) return;