Restore in process embedding to NavigableContents.

This code is being restored after having been removed from:
https://chromium-review.googlesource.com/c/chromium/src/+/1603743

Only change to restored code is to remove any |use_window_service|
params/codepaths that were present in the originally removed version.

This fixes a regression in Assistant which prevented Assistant Settings
and cards (implemented using NavigableContents) from rendering to the
user.

Bug: b:132717712
Change-Id: I27f3595f8e25bcf91664ea27beec27bf39855a31
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1613723Reviewed-by: Ken Rockot <rockot@google.com>
Reviewed-by: Scott Violet <sky@chromium.org>
Reviewed-by: Tom Sepez <tsepez@chromium.org>
Commit-Queue: David Black <dmblack@google.com>
Cr-Commit-Position: refs/heads/master@{#660684}

services/content/navigable_contents_impl.cc

@@ -48,6 +48,16 @@ void NavigableContentsImpl::GoBack(
   delegate_->GoBack(std::move(callback));
 }
 
+void NavigableContentsImpl::CreateView(CreateViewCallback callback) {
+  // Create and stash a new callback (indexed by token) which the in-process
+  // client library can use to establish an "embedding" of the contents' view.
+  auto token = base::UnguessableToken::Create();
+  NavigableContentsView::RegisterInProcessEmbedCallback(
+      token, base::BindOnce(&NavigableContentsImpl::EmbedInProcessClientView,
+                            weak_ptr_factory_.GetWeakPtr()));
+  std::move(callback).Run(token);
+}
+
 void NavigableContentsImpl::Focus() {
   delegate_->Focus();
 }
@@ -56,4 +66,18 @@ void NavigableContentsImpl::FocusThroughTabTraversal(bool reverse) {
   delegate_->FocusThroughTabTraversal(reverse);
 }
 
+void NavigableContentsImpl::EmbedInProcessClientView(
+    NavigableContentsView* view) {
+  DCHECK(native_content_view_);
+#if defined(TOOLKIT_VIEWS) && defined(USE_AURA)
+  view->native_view()->AddChild(native_content_view_);
+  native_content_view_->Show();
+#else
+  // TODO(https://crbug.com/855092): Support embedding of other native client
+  // views without Views + Aura.
+  NOTREACHED()
+      << "NavigableContents views are currently only supported on Views UI.";
+#endif
+}
+
 }  // namespace content

services/content/navigable_contents_impl.h

@@ -20,6 +20,7 @@ namespace content {
 
 class Service;
 class NavigableContentsDelegate;
+class NavigableContentsView;
 
 // This is the state which backs an individual NavigableContents owned by some
 // client of the Content Service. In terms of the classical Content API, this is
@@ -37,9 +38,14 @@ class NavigableContentsImpl : public mojom::NavigableContents {
   // mojom::NavigableContents:
   void Navigate(const GURL& url, mojom::NavigateParamsPtr params) override;
   void GoBack(mojom::NavigableContents::GoBackCallback callback) override;
+  void CreateView(CreateViewCallback callback) override;
   void Focus() override;
   void FocusThroughTabTraversal(bool reverse) override;
 
+  // Used (indirectly) by the client library when run in the same process as the
+  // service. See the |CreateView()| implementation for details.
+  void EmbedInProcessClientView(NavigableContentsView* view);
+
   Service* const service_;
 
   mojo::Receiver<mojom::NavigableContents> receiver_;

services/content/public/cpp/navigable_contents.cc

@@ -34,6 +34,8 @@ void NavigableContents::RemoveObserver(NavigableContentsObserver* observer) {
 NavigableContentsView* NavigableContents::GetView() {
   if (!view_) {
     view_ = base::WrapUnique(new NavigableContentsView(this));
+    contents_->CreateView(base::BindOnce(
+        &NavigableContents::OnEmbedTokenReceived, base::Unretained(this)));
   }
   return view_.get();
 }
@@ -99,4 +101,10 @@ void NavigableContents::UpdateContentAXTree(const ui::AXTreeID& id) {
     view_->NotifyAccessibilityTreeChange();
 }
 
+void NavigableContents::OnEmbedTokenReceived(
+    const base::UnguessableToken& token) {
+  DCHECK(view_);
+  view_->EmbedUsingToken(token);
+}
+
 }  // namespace content

services/content/public/cpp/navigable_contents.h

@@ -85,6 +85,8 @@ class COMPONENT_EXPORT(CONTENT_SERVICE_CPP) NavigableContents
                              bool from_user_gesture) override;
   void UpdateContentAXTree(const ui::AXTreeID& id) override;
 
+  void OnEmbedTokenReceived(const base::UnguessableToken& token);
+
   mojo::Remote<mojom::NavigableContents> contents_;
   mojo::Receiver<mojom::NavigableContentsClient> client_receiver_;
   std::unique_ptr<NavigableContentsView> view_;

services/content/public/cpp/navigable_contents_view.cc

@@ -4,6 +4,8 @@
 
 #include "services/content/public/cpp/navigable_contents_view.h"
 
+#include <map>
+
 #include "base/bind_helpers.h"
 #include "base/callback.h"
 #include "base/no_destructor.h"
@@ -28,6 +30,15 @@ namespace content {
 
 namespace {
 
+using InProcessEmbeddingMap =
+    std::map<base::UnguessableToken,
+             base::OnceCallback<void(NavigableContentsView*)>>;
+
+InProcessEmbeddingMap& GetInProcessEmbeddingMap() {
+  static base::NoDestructor<InProcessEmbeddingMap> embedding_map;
+  return *embedding_map;
+}
+
 base::AtomicFlag& GetInServiceProcessFlag() {
   static base::NoDestructor<base::AtomicFlag> in_service_process;
   return *in_service_process;
@@ -144,4 +155,34 @@ NavigableContentsView::NavigableContentsView(NavigableContents* contents)
 #endif  // defined(TOOLKIT_VIEWS) && defined(USE_AURA)
 }
 
+void NavigableContentsView::EmbedUsingToken(
+    const base::UnguessableToken& token) {
+#if defined(TOOLKIT_VIEWS)
+  DCHECK(IsClientRunningInServiceProcess());
+
+  // |token| should already have an embed callback entry in the in-process
+  // callback map, injected by the in-process Content Service implementation.
+  auto& embeddings = GetInProcessEmbeddingMap();
+  auto it = embeddings.find(token);
+  if (it == embeddings.end()) {
+    DLOG(ERROR) << "Unable to embed with unknown token " << token.ToString();
+    return;
+  }
+
+  // Invoke a callback provided by the Content Service's host environment. This
+  // should parent a web content view to our own |view()|, as well as set
+  // |native_view_| to the corresponding web contents' own NativeView.
+  auto callback = std::move(it->second);
+  embeddings.erase(it);
+  std::move(callback).Run(this);
+#endif  // defined(TOOLKIT_VIEWS)
+}
+
+// static
+void NavigableContentsView::RegisterInProcessEmbedCallback(
+    const base::UnguessableToken& token,
+    base::OnceCallback<void(NavigableContentsView*)> callback) {
+  GetInProcessEmbeddingMap()[token] = std::move(callback);
+}
+
 }  // namespace content

services/content/public/cpp/navigable_contents_view.h

@@ -9,6 +9,7 @@
 
 #include "base/callback.h"
 #include "base/component_export.h"
+#include "base/unguessable_token.h"
 #include "ui/gfx/native_widget_types.h"
 
 #if defined(TOOLKIT_VIEWS) && defined(USE_AURA)
@@ -66,6 +67,16 @@ class COMPONENT_EXPORT(CONTENT_SERVICE_CPP) NavigableContentsView {
 
   explicit NavigableContentsView(NavigableContents* contents_);
 
+  // Establishes a hierarchical relationship between this view's native UI
+  // object and another native UI object within the Content Service.
+  void EmbedUsingToken(const base::UnguessableToken& token);
+
+  // Used by the service directly when running in the same process. Establishes
+  // a way for an embed token to be used without the UI service.
+  static void RegisterInProcessEmbedCallback(
+      const base::UnguessableToken& token,
+      base::OnceCallback<void(NavigableContentsView*)> callback);
+
   NavigableContents* const contents_;
 
 #if defined(TOOLKIT_VIEWS) && defined(USE_AURA)

services/content/public/cpp/test/fake_navigable_contents.cc

@@ -6,6 +6,7 @@
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
+#include "base/unguessable_token.h"
 #include "services/content/public/cpp/navigable_contents_view.h"
 #include "services/content/public/cpp/test/fake_navigable_contents_factory.h"
 
@@ -42,6 +43,13 @@ void FakeNavigableContents::GoBack(
   std::move(callback).Run(false /* success */);
 }
 
+void FakeNavigableContents::CreateView(CreateViewCallback callback) {
+  auto token = base::UnguessableToken::Create();
+  NavigableContentsView::RegisterInProcessEmbedCallback(token,
+                                                        base::DoNothing());
+  std::move(callback).Run(token);
+}
+
 void FakeNavigableContents::Focus() {}
 
 void FakeNavigableContents::FocusThroughTabTraversal(bool reverse) {}

services/content/public/cpp/test/fake_navigable_contents.h

@@ -40,6 +40,7 @@ class FakeNavigableContents : public mojom::NavigableContents {
   // mojom::NavigableContents:
   void Navigate(const GURL& url, mojom::NavigateParamsPtr params) override;
   void GoBack(mojom::NavigableContents::GoBackCallback callback) override;
+  void CreateView(CreateViewCallback callback) override;
   void Focus() override;
   void FocusThroughTabTraversal(bool reverse) override;
 

services/content/public/mojom/navigable_contents.mojom

@@ -8,6 +8,7 @@ import "services/network/public/mojom/network_param.mojom";
 import "ui/accessibility/mojom/ax_tree_id.mojom";
 import "ui/base/mojo/window_open_disposition.mojom";
 import "ui/gfx/geometry/mojo/geometry.mojom";
+import "mojo/public/mojom/base/unguessable_token.mojom";
 import "url/mojom/url.mojom";
 
 // Parameters used to configure the behavior of |NavigableContents.Navigate|.
@@ -31,6 +32,12 @@ interface NavigableContents {
   // navigation attempt will fail if the history stack is empty.
   GoBack() => (bool success);
 
+  // Creates a visual representation of the navigated contents, which is
+  // maintained by the Content Service. Responds with a |embed_token| which can
+  // be given to Mus in order to authorize embedding of that visual
+  // representation within the client application's own window tree.
+  CreateView() => (mojo_base.mojom.UnguessableToken embed_token);
+
   // Attempts to transfer global input focus to the navigated contents if they
   // have an active visual representation.
   Focus();