[Contextual Search] Remove layers when no longer needed.

Now that there can be multiple Overlays Panels being used,
a few bugs are happening due to the Panel's cc::Layer not
being properly removed.

This CL fixes the problem by removing the layer when a
OverlayPanel shows up when another one is being displayed.

Also, this CL removed the OverlayPanel layer from the
StaticLayout whenever that layout gets hidden (see
dettachViews method).

BUG=539847

Review URL: https://codereview.chromium.org/1489213002

Cr-Commit-Position: refs/heads/master@{#363092}
(cherry picked from commit a53e46e)

Review URL: https://codereview.chromium.org/1502703002 .

Cr-Commit-Position: refs/branch-heads/2564@{#242}
Cr-Branched-From: 1283eca-refs/heads/master@{#359700}

chrome/android/java/src/org/chromium/chrome/browser/compositor/bottombar/OverlayPanel.java

@@ -158,6 +158,8 @@ public boolean isExpanded() {
 
     @Override
     public void closePanel(StateChangeReason reason, boolean animate) {
+        if (!isShowing()) return;
+
         super.closePanel(reason, animate);
 
         // If the close action is animated, the Layout will be hidden when
@@ -173,6 +175,8 @@ public void closePanel(StateChangeReason reason, boolean animate) {
      * @param reason The reason the panel is being shown.
      */
     public void requestPanelShow(StateChangeReason reason) {
+        if (isShowing()) return;
+
         if (mPanelManager != null) {
             mPanelManager.requestPanelShow(this, reason);
         }

chrome/browser/android/compositor/scene_layer/static_tab_scene_layer.cc

@@ -125,14 +125,24 @@ void StaticTabSceneLayer::SetContentSceneLayer(JNIEnv* env,
                                                jobject jobj,
                                                jobject jcontent_scene_layer) {
   SceneLayer* content_scene_layer = FromJavaObject(env, jcontent_scene_layer);
-  if (content_scene_layer && content_scene_layer->layer()) {
-    content_scene_layer_ = content_scene_layer->layer();
-    if (content_scene_layer_.get())
-      layer_->AddChild(content_scene_layer_);
-  } else if (content_scene_layer_) {
+  scoped_refptr<cc::Layer> layer = content_scene_layer ?
+      content_scene_layer->layer() : nullptr;
+
+  if (content_scene_layer_ && content_scene_layer_ != layer) {
     content_scene_layer_->RemoveFromParent();
     content_scene_layer_ = nullptr;
   }
+
+  // TODO(pedrosimonetti): Consider being smarter with regards to when to
+  // add the layer to the hierarchy. For now, we need to keep adding the
+  // content_scene_layer on every frame because the content_layer is also
+  // added on every frame. This means that if we only add it once, the
+  // content_layer will be added again on the next frame and will
+  // occlude the content_scene_layer.
+  if (layer) {
+    content_scene_layer_ = layer;
+    layer_->AddChild(layer);
+  }
 }
 
 static jlong Init(JNIEnv* env, const JavaParamRef<jobject>& jobj) {