Introduce ViewRoot forwarding input/view events to native

chrome/android/java/src/org/chromium/chrome/browser/tab/Tab.java

Index: chrome/android/java/src/org/chromium/chrome/browser/tab/Tab.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/tab/Tab.java b/chrome/android/java/src/org/chromium/chrome/browser/tab/Tab.java
index 699d62ed8f1c24ab7666633e9e6b27b154d95428..44efdba735ca4cca40e0ac4b1927d6dfd26d95d7 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/tab/Tab.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/tab/Tab.java
@@ -107,6 +107,7 @@ import org.chromium.printing.PrintingControllerImpl;
 import org.chromium.ui.base.LocalizationUtils;
 import org.chromium.ui.base.PageTransition;
 import org.chromium.ui.base.ViewAndroidDelegate;
+import org.chromium.ui.base.ViewRoot;
 import org.chromium.ui.base.WindowAndroid;
 import org.chromium.ui.mojom.WindowOpenDisposition;
 
@@ -187,6 +188,9 @@ public class Tab implements ViewGroup.OnHierarchyChangeListener,
     /** {@link ContentViewCore} showing the current page, or {@code null} if the tab is frozen. */
     private ContentViewCore mContentViewCore;
 
+    /** {@link ViewRoot} used to forward input/view events down to native. */
+    private ViewRoot mViewRoot;
+
     /** Listens to gesture events fired by the ContentViewCore. */
     private GestureStateListener mGestureStateListener;
 
@@ -1523,7 +1527,7 @@ public class Tab implements ViewGroup.OnHierarchyChangeListener,
             // TODO(yusufo): We can't call updateWindowAndroid here and set mWindowAndroid to null
             // because many code paths (including navigation) expect the tab to always be associated
             // with an activity, and will crash. crbug.com/657007
-            if (mContentViewCore != null) mContentViewCore.updateWindowAndroid(null);
+            if (mContentViewCore != null) mContentViewCore.updateViewRoot(null);
             attachTabContentManager(null);
         }
 
@@ -1584,7 +1588,13 @@ public class Tab implements ViewGroup.OnHierarchyChangeListener,
         // TODO(yusufo): mWindowAndroid can never be null until crbug.com/657007 is fixed.
         assert windowAndroid != null;
         mWindowAndroid = windowAndroid;
-        if (mContentViewCore != null) mContentViewCore.updateWindowAndroid(mWindowAndroid);
+        if (mContentViewCore != null) {
+            // Create a new ViewRoot for the updated WindowAndroid.
+            ViewRoot viewRoot = ViewRoot.create(mWindowAndroid);
+            mContentViewCore.updateViewRoot(viewRoot);
+            mViewRoot.destroy();
+            mViewRoot = viewRoot;
+        }
     }
 
     /**
@@ -1625,6 +1635,13 @@ public class Tab implements ViewGroup.OnHierarchyChangeListener,
     }
 
     /**
+     * @return {@link ViewRoot} instance used to forward view/input events.
+     */
+    public ViewRoot getViewRoot() {
+        return mViewRoot;
+    }
+
+    /**
      * Called when a navigation begins and no navigation was in progress
      * @param toDifferentDocument Whether this navigation will transition between
      * documents (i.e., not a fragment navigation or JS History API call).
@@ -1720,7 +1737,7 @@ public class Tab implements ViewGroup.OnHierarchyChangeListener,
         cv.setContentDescription(mThemedApplicationContext.getResources().getString(
                 R.string.accessibility_content_view));
         cvc.initialize(ViewAndroidDelegate.createBasicDelegate(cv), cv, webContents,
-                getWindowAndroid());
+                ViewRoot.create(mWindowAndroid));
         ChromeActionModeCallback actionModeCallback = new ChromeActionModeCallback(
                 mThemedApplicationContext, this, cvc.getActionModeCallbackHelper());
         cvc.setActionModeCallback(actionModeCallback);
@@ -1749,6 +1766,7 @@ public class Tab implements ViewGroup.OnHierarchyChangeListener,
             }
 
             mContentViewCore = cvc;
+            mViewRoot = cvc.getViewRoot();
             cvc.getContainerView().setOnHierarchyChangeListener(this);
             cvc.getContainerView().setOnSystemUiVisibilityChangeListener(this);
 
@@ -2343,6 +2361,9 @@ public class Tab implements ViewGroup.OnHierarchyChangeListener,
         mContentViewCore.destroy();
         mContentViewCore = null;
 
+        mViewRoot.destroy();
+        mViewRoot = null;
+
         mWebContentsDelegate = null;
 
         if (mWebContentsObserver != null) {
@@ -2459,7 +2480,7 @@ public class Tab implements ViewGroup.OnHierarchyChangeListener,
         // (see http://crbug.com/340987).
         newContentViewCore.onSizeChanged(originalWidth, originalHeight, 0, 0);
         if (!bounds.isEmpty()) {
-            newContentViewCore.getWindowAndroid().getViewRoot().onPhysicalBackingSizeChanged(
+            newContentViewCore.getViewRoot().onPhysicalBackingSizeChanged(
                     bounds.right, bounds.bottom);
         }
         newContentViewCore.onShow();