Introduce blink::mojom:::RemoteMainFrame interface

... and binding logic, pPreparation work for migrating
PageMsg_UpdateTextAutosizerPageInfoForRemoteMainFrames to Mojom.

This CL is a preparing CL that binds blink::RemoteFrame instances to
blink::mojom::RemoteFrameFrame interface, when it is appropriate.
It makes use of the existing WebViewImpl::DidAttachRemoteMainFrame() hook.

BUG=1102440
R=dtapuska@chromium.org

Change-Id: I792f26f38070dc9a168c0c76081941450243a5f5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2307152Reviewed-by: Dave Tapuska <dtapuska@chromium.org>
Reviewed-by: Dominick Ng <dominickn@chromium.org>
Commit-Queue: Dominick Ng <dominickn@chromium.org>
Auto-Submit: Antonio Gomes <tonikitoo@igalia.com>
Cr-Commit-Position: refs/heads/master@{#790199}

third_party/blink/public/mojom/frame/frame.mojom

@@ -885,6 +885,17 @@ interface LocalMainFrame {
       pending_remote<network.mojom.CrossOriginOpenerPolicyReporter> reporter);
 };
 
+// Implemented in Blink, this interface defines remote main-frame-specific
+// methods that will be invoked from the browser process (e.g.
+// content::RenderFrameProxyHost).
+//
+// There is only ever one remote main frame for a given tab in all renderer
+// processes.
+//
+// This interface will only be provided when the RemoteFrame is a main frame.
+interface RemoteMainFrame {
+};
+
 // Implemented in Browser, this interface defines local-main-frame-specific
 // methods that will be invoked from the renderer process (e.g. WebViewImpl).
 interface LocalMainFrameHost {

third_party/blink/renderer/core/exported/web_view_impl.cc

@@ -2010,7 +2010,7 @@ void WebViewImpl::DidAttachRemoteMainFrame() {
   DCHECK(!MainFrameImpl());
 
   RemoteFrame* remote_frame = DynamicTo<RemoteFrame>(GetPage()->MainFrame());
-  DCHECK(remote_frame);
+  remote_frame->WasAttachedAsRemoteMainFrame();
 
   remote_frame->GetRemoteAssociatedInterfaces()->GetInterface(
       remote_main_frame_host_remote_.BindNewEndpointAndPassReceiver());

third_party/blink/renderer/core/frame/remote_frame.cc

@@ -95,7 +95,10 @@ RemoteFrame::RemoteFrame(
             owner,
             frame_token,
             MakeGarbageCollected<RemoteWindowProxyManager>(*this),
-            inheriting_agent_factory) {
+            inheriting_agent_factory),
+      interface_registry_(
+          interface_registry ? interface_registry
+                             : InterfaceRegistry::GetEmptyInterfaceRegistry()) {
   // TODO(crbug.com/1094850): Remove this check once the renderer is correctly
   // handling errors during the creation of HTML portal elements, which would
   // otherwise cause RemoteFrame() being created with empty frame tokens.
@@ -225,6 +228,7 @@ void RemoteFrame::DetachImpl(FrameDetachType type) {
   if (cc_layer_)
     SetCcLayer(nullptr, false, false);
   receiver_.reset();
+  main_frame_receiver_.reset();
 }
 
 bool RemoteFrame::DetachDocument() {
@@ -723,6 +727,11 @@ void RemoteFrame::SetOpener(Frame* opener_frame) {
   }
 }
 
+void RemoteFrame::WasAttachedAsRemoteMainFrame() {
+  interface_registry_->AddAssociatedInterface(WTF::BindRepeating(
+      &RemoteFrame::BindToMainFrameReceiver, WrapWeakPersistent(this)));
+}
+
 bool RemoteFrame::IsIgnoredForHitTest() const {
   HTMLFrameOwnerElement* owner = DeprecatedLocalOwner();
   if (!owner || !owner->GetLayoutObject())
@@ -791,10 +800,17 @@ void RemoteFrame::ApplyReplicatedFeaturePolicyHeader() {
 }
 
 void RemoteFrame::BindToReceiver(
-    blink::RemoteFrame* frame,
+    RemoteFrame* frame,
     mojo::PendingAssociatedReceiver<mojom::blink::RemoteFrame> receiver) {
   DCHECK(frame);
   frame->receiver_.Bind(std::move(receiver));
 }
 
+void RemoteFrame::BindToMainFrameReceiver(
+    RemoteFrame* frame,
+    mojo::PendingAssociatedReceiver<mojom::blink::RemoteMainFrame> receiver) {
+  DCHECK(frame);
+  frame->main_frame_receiver_.Bind(std::move(receiver));
+}
+
 }  // namespace blink

third_party/blink/renderer/core/frame/remote_frame.h

@@ -33,6 +33,7 @@ class RemoteFrameClient;
 struct FrameLoadRequest;
 
 class CORE_EXPORT RemoteFrame final : public Frame,
+                                      public mojom::blink::RemoteMainFrame,
                                       public mojom::blink::RemoteFrame {
  public:
   // Returns the RemoteFrame for the given |frame_token|.
@@ -169,6 +170,9 @@ class CORE_EXPORT RemoteFrame final : public Frame,
 
   void SetOpener(Frame* opener) override;
 
+  // Indicate that this frame was attached as a MainFrame.
+  void WasAttachedAsRemoteMainFrame();
+
  private:
   // Frame protected overrides:
   void DetachImpl(FrameDetachType) override;
@@ -182,8 +186,11 @@ class CORE_EXPORT RemoteFrame final : public Frame,
   void ApplyReplicatedFeaturePolicyHeader();
 
   static void BindToReceiver(
-      blink::RemoteFrame* frame,
+      RemoteFrame* frame,
       mojo::PendingAssociatedReceiver<mojom::blink::RemoteFrame> receiver);
+  static void BindToMainFrameReceiver(
+      RemoteFrame* frame,
+      mojo::PendingAssociatedReceiver<mojom::blink::RemoteMainFrame> receiver);
 
   Member<RemoteFrameView> view_;
   RemoteSecurityContext security_context_;
@@ -193,9 +200,13 @@ class CORE_EXPORT RemoteFrame final : public Frame,
   ParsedFeaturePolicy feature_policy_header_;
   String unique_name_;
 
+  InterfaceRegistry* const interface_registry_;
+
   mojo::AssociatedRemote<mojom::blink::RemoteFrameHost>
       remote_frame_host_remote_;
   mojo::AssociatedReceiver<mojom::blink::RemoteFrame> receiver_{this};
+  mojo::AssociatedReceiver<mojom::blink::RemoteMainFrame> main_frame_receiver_{
+      this};
 };
 
 inline RemoteFrameView* RemoteFrame::View() const {