Allow adding an overlay not attached to the tab layer

Currently any overlay ContentViewCore added to the Tab is
automatically added to the Tab CC layer.

This CL introduces a new parameter to allow romaing overlays.

BUG=453121

Review URL: https://codereview.chromium.org/1026983002

Cr-Commit-Position: refs/heads/master@{#322269}

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

@@ -1398,24 +1398,35 @@ public class Tab implements ViewGroup.OnHierarchyChangeListener,
     }
 
     /**
-     * Adds a {@link ContentViewCore} to this {@link Tab} as an overlay object.  This
-     * {@link ContentViewCore} will be attached to the CC layer hierarchy and have all layout events
-     * propagated to it.  This {@link ContentViewCore} can be removed via
+     * Adds a {@link ContentViewCore} to this {@link Tab} as an overlay object.
+     * If attachLayer is set, the {@link ContentViewCore} will be attached to CC layer hierarchy.
+     * This {@link ContentViewCore} will have all layout events propagated to it.
+     * This {@link ContentViewCore} can be removed via
      * {@link #detachOverlayContentViewCore(ContentViewCore)}.
      * @param content The {@link ContentViewCore} to attach.
      * @param visible Whether or not to make the content visible.
+     * @param attachLayer Whether or not to attach the content view to the CC layer hierarchy.
      */
-    public void attachOverlayContentViewCore(ContentViewCore content, boolean visible) {
+    public void attachOverlayContentViewCore(
+            ContentViewCore content, boolean visible, boolean attachLayer) {
         if (content == null) return;
 
         assert !mOverlayContentViewCores.contains(content);
         mOverlayContentViewCores.add(content);
-        nativeAttachOverlayContentViewCore(mNativeTabAndroid, content, visible);
+        if (attachLayer) nativeAttachOverlayContentViewCore(mNativeTabAndroid, content, visible);
         for (TabObserver observer : mObservers) {
             observer.onOverlayContentViewCoreAdded(this, content);
         }
     }
 
+    /**
+     * TODO(aruslan): remove this.
+     * Temporary overload to avoid 2-way commit.
+     */
+    public void attachOverlayContentViewCore(ContentViewCore content, boolean visible) {
+        attachOverlayContentViewCore(content, visible, true);
+    }
+
     /**
      * Removes a {@link ContentViewCore} overlay object from this {@link Tab}.  This
      * {@link ContentViewCore} must have previously been added via

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

@@ -612,7 +612,7 @@ public class TransitionPageHelper extends EmptyTabObserver {
 
         mTransitionObserver = createTransitionObserver();
 
-        if (mTab != null) mTab.attachOverlayContentViewCore(mTransitionContentViewCore, true);
+        if (mTab != null) mTab.attachOverlayContentViewCore(mTransitionContentViewCore, true, true);
 
         nativeSetWebContents(mNativeTransitionPageHelperPtr, mTransitionContentViewCore);
         setTransitionOpacity(0.0f);

chrome/browser/android/tab_android.cc

@@ -844,7 +844,8 @@ void TabAndroid::DetachOverlayContentViewCore(JNIEnv* env,
                                                          jcontent_view_core);
   DCHECK(content_view_core);
 
-  content_view_core->GetLayer()->RemoveFromParent();
+  if (content_view_core->GetLayer()->parent() == content_layer_)
+    content_view_core->GetLayer()->RemoveFromParent();
 }
 
 static void Init(JNIEnv* env, jobject obj) {