Remove unneeded calls to plugin.SetParentVisible.

Plugin (WebPluginContainerImpl) does not keep its own state about
visibility of parent, and once it is no longer inheriting from
FrameViewBase, it will not implement any ParentVisible methods.
If required, it could always call parent_.IsVisible.

BUG=637460

Review-Url: https://codereview.chromium.org/2808723002
Cr-Commit-Position: refs/heads/master@{#463409}

third_party/WebKit/Source/core/frame/FrameView.cpp

@@ -4729,9 +4729,6 @@ void FrameView::SetParentVisible(bool visible) {
 
   for (const auto& child : children_)
     child->SetParentVisible(visible);
-
-  for (const auto& plugin : plugins_)
-    plugin->SetParentVisible(visible);
 }
 
 void FrameView::Show() {
@@ -4752,9 +4749,6 @@ void FrameView::Show() {
     if (IsParentVisible()) {
       for (const auto& child : children_)
         child->SetParentVisible(true);
-
-      for (const auto& plugin : plugins_)
-        plugin->SetParentVisible(true);
     }
   }
 
@@ -4766,9 +4760,6 @@ void FrameView::Hide() {
     if (IsParentVisible()) {
       for (const auto& child : children_)
         child->SetParentVisible(false);
-
-      for (const auto& plugin : plugins_)
-        plugin->SetParentVisible(false);
     }
     SetSelfVisible(false);
     if (ScrollingCoordinator* scrolling_coordinator =