Implement NativeViewHostAura::InstallClip.

content/browser/web_contents/web_contents_view_aura.cc

Index: content/browser/web_contents/web_contents_view_aura.cc
diff --git a/content/browser/web_contents/web_contents_view_aura.cc b/content/browser/web_contents/web_contents_view_aura.cc
index 772d2afea3cf78f5ac661eedfca3c43a4cc0bddb..3267145cdfa38b5eb927234f57a320de82f8ea8f 100644
--- a/content/browser/web_contents/web_contents_view_aura.cc
+++ b/content/browser/web_contents/web_contents_view_aura.cc
@@ -558,6 +558,12 @@ class WebContentsViewAura::WindowObserver
                                      aura::Window* parent) OVERRIDE {
     if (window != view_->window_)
       return;
+
+    // Since all native views are hosted inside a clipping window, the actual
+    // parent that we care about is the clipping window's parent.
+    if (parent)

[sky, 2014/06/16 17:11:03]

That a different parent exists is an implementation detail of NativeViewHost. If
that changes this code will break and we may now know. We need a better way to
be insulated from changes in NativeViewHost. Maybe a method on NativeViewHost?

[calamity, 2014/06/17 05:01:12]

Since this operates at the window level, I don't think there's a way to ask the
relevant NativeViewHost about this. Maybe a static method that checks if the
window name matches the clipping window's name?

Another option is to static_cast the NativeViewHost out of the window's
kHostViewKey and use host->GetWidget()->GetNativeView().

[sky, 2014/06/17 16:25:25]

Neither of these options work since this code shouldn't know about views. Also,
since this code isn't necessarily used with views assuming views is being used
is equally wrong. Also, isn't the code in UpdateConstrainedWindow going to
incorrectly consider the clipping window?

I think we're going to need some way to tag (similar to kHostViewKey) which
parent is used but is exposed in a place this code can access.

+      parent = parent->parent();
+
     if (parent_)
       parent_->RemoveObserver(this);
 
@@ -673,7 +679,7 @@ class WebContentsViewAura::WindowObserver
     if (parent_) {
       const aura::Window::Windows& children = parent_->children();
       for (size_t i = 0; i < children.size(); ++i) {
-        if (children[i] != view_->window_ &&
+        if (children[i] != view_->window_->parent() &&
             children[i] != exclude &&
             children[i]->IsVisible()) {
           constrained_windows.push_back(children[i]->GetBoundsInRootWindow());