chrome: Add support for Alloy style browsers and windows (see #3681)

Split the Alloy runtime into bootstrap and style components. Support
creation of Alloy style browsers and windows with the Chrome runtime.
Chrome runtime (`--enable-chrome-runtime`) + Alloy style
(`--use-alloy-style`) supports Views (`--use-views`), native parent
(`--use-native`) and windowless rendering
(`--off-screen-rendering-enabled`).

Print preview is supported in all cases except with windowless rendering
on all platforms and native parent on MacOS. It is disabled by default
with Alloy style for legacy compatibility. Where supported it can be
enabled or disabled globally using `--[enable|disable]-print-preview` or
configured on a per-RequestContext basis using the
`printing.print_preview_disabled` preference. It also behaves as
expected when triggered via the PDF viewer print button.

Chrome runtime + Alloy style behavior differs from Alloy runtime in the
following significant ways:

- Supports Chrome error pages by default.
- DevTools popups are Chrome style only (cannot be windowless).
- The Alloy extension API will not supported.

Chrome runtime + Alloy style passes all expected Alloy ceftests except
the following:

- `DisplayTest.AutoResize` (Alloy extension API not supported)
- `DownloadTest.*` (Download API not yet supported)
- `ExtensionTest.*` (Alloy extension API not supported)

This change also adds Chrome runtime support for
CefContextMenuHandler::RunContextMenu (see #3293).

This change also explicitly blocks (and doesn't retry) FrameAttached
requests from PDF viewer and print preview excluded frames (see #3664).

Known issues specific to Chrome runtime + Alloy style:
- DevTools popup with windowless rendering doesn't load successfully.
  Use windowed rendering or remote debugging as a workaround.
- Chrome style Window with Alloy style BrowserView (`--use-alloy-style
  --use-chrome-style-window`) does not show Chrome theme changes.

To test:
- Run `ceftests --enable-chrome-runtime --use-alloy-style
       [--use-chrome-style-window] [--use-views|--use-native]
       --gtest_filter=...`
- Run `cefclient --enable-chrome-runtime --use-alloy-style
       [--use-chrome-style-window]
       [--use-views|--use-native|--off-screen-rendering-enabled]`
- Run `cefsimple --enable-chrome-runtime --use-alloy-style [--use-views]`

libcef/browser/chrome/chrome_context_menu_handler.cc

@@ -4,6 +4,9 @@
 
 #include "libcef/browser/chrome/chrome_context_menu_handler.h"
 
+#include "base/memory/weak_ptr.h"
+
+#include "libcef/browser/alloy/alloy_browser_host_impl.h"
 #include "libcef/browser/browser_host_base.h"
 #include "libcef/browser/context_menu_params_impl.h"
 #include "libcef/browser/simple_menu_model_impl.h"
@@ -14,6 +17,64 @@ namespace context_menu {
 
 namespace {
 
+constexpr int kInvalidCommandId = -1;
+const cef_event_flags_t kEmptyEventFlags = static_cast<cef_event_flags_t>(0);
+
+class CefRunContextMenuCallbackImpl : public CefRunContextMenuCallback {
+ public:
+  using Callback =
+      base::OnceCallback<void(int /*command_id*/, int /*event_flags*/)>;
+
+  explicit CefRunContextMenuCallbackImpl(Callback callback)
+      : callback_(std::move(callback)) {}
+
+  CefRunContextMenuCallbackImpl(const CefRunContextMenuCallbackImpl&) = delete;
+  CefRunContextMenuCallbackImpl& operator=(
+      const CefRunContextMenuCallbackImpl&) = delete;
+
+  ~CefRunContextMenuCallbackImpl() override {
+    if (!callback_.is_null()) {
+      // The callback is still pending. Cancel it now.
+      if (CEF_CURRENTLY_ON_UIT()) {
+        RunNow(std::move(callback_), kInvalidCommandId, kEmptyEventFlags);
+      } else {
+        CEF_POST_TASK(CEF_UIT,
+                      base::BindOnce(&CefRunContextMenuCallbackImpl::RunNow,
+                                     std::move(callback_), kInvalidCommandId,
+                                     kEmptyEventFlags));
+      }
+    }
+  }
+
+  void Continue(int command_id, cef_event_flags_t event_flags) override {
+    if (CEF_CURRENTLY_ON_UIT()) {
+      if (!callback_.is_null()) {
+        RunNow(std::move(callback_), command_id, event_flags);
+        callback_.Reset();
+      }
+    } else {
+      CEF_POST_TASK(CEF_UIT,
+                    base::BindOnce(&CefRunContextMenuCallbackImpl::Continue,
+                                   this, command_id, event_flags));
+    }
+  }
+
+  void Cancel() override { Continue(kInvalidCommandId, kEmptyEventFlags); }
+
+  bool IsDisconnected() const { return callback_.is_null(); }
+  void Disconnect() { callback_.Reset(); }
+
+ private:
+  static void RunNow(Callback callback, int command_id, int event_flags) {
+    CEF_REQUIRE_UIT();
+    std::move(callback).Run(command_id, event_flags);
+  }
+
+  Callback callback_;
+
+  IMPLEMENT_REFCOUNTING(CefRunContextMenuCallbackImpl);
+};
+
 // Lifespan is controlled by RenderViewContextMenu.
 class CefContextMenuObserver : public RenderViewContextMenuObserver,
                                public CefSimpleMenuModelImpl::StateDelegate {
@@ -21,7 +82,10 @@ class CefContextMenuObserver : public RenderViewContextMenuObserver,
   CefContextMenuObserver(RenderViewContextMenu* context_menu,
                          CefRefPtr<CefBrowserHostBase> browser,
                          CefRefPtr<CefContextMenuHandler> handler)
-      : context_menu_(context_menu), browser_(browser), handler_(handler) {}
+      : context_menu_(context_menu), browser_(browser), handler_(handler) {
+    // This remains valid until the next time a context menu is created.
+    browser_->set_context_menu_observer(this);
+  }
 
   CefContextMenuObserver(const CefContextMenuObserver&) = delete;
   CefContextMenuObserver& operator=(const CefContextMenuObserver&) = delete;
@@ -130,6 +194,29 @@ class CefContextMenuObserver : public RenderViewContextMenuObserver,
     }
   }
 
+  bool HandleShow() {
+    if (model_->GetCount() == 0) {
+      return false;
+    }
+
+    CefRefPtr<CefRunContextMenuCallbackImpl> callbackImpl(
+        new CefRunContextMenuCallbackImpl(
+            base::BindOnce(&CefContextMenuObserver::ExecuteCommandCallback,
+                           weak_ptr_factory_.GetWeakPtr())));
+
+    bool handled = handler_->RunContextMenu(browser_, GetFrame(), params_,
+                                            model_, callbackImpl.get());
+    if (!handled && callbackImpl->IsDisconnected()) {
+      LOG(ERROR) << "Should return true from RunContextMenu when executing the "
+                    "callback";
+      handled = true;
+    }
+    if (!handled) {
+      callbackImpl->Disconnect();
+    }
+    return handled;
+  }
+
  private:
   struct ItemInfo {
     ItemInfo() = default;
@@ -169,6 +256,7 @@ class CefContextMenuObserver : public RenderViewContextMenuObserver,
     // May return nullptr if the frame is destroyed while the menu is pending.
     auto* rfh = context_menu_->GetRenderFrameHost();
     if (rfh) {
+      // May return nullptr for guest views.
       frame = browser_->GetFrameForHost(rfh);
     }
     if (!frame) {
@@ -177,6 +265,14 @@ class CefContextMenuObserver : public RenderViewContextMenuObserver,
     return frame;
   }
 
+  void ExecuteCommandCallback(int command_id, int event_flags) {
+    if (command_id != kInvalidCommandId) {
+      context_menu_->ExecuteCommand(command_id, event_flags);
+    }
+    context_menu_->Cancel();
+    OnMenuClosed();
+  }
+
   RenderViewContextMenu* const context_menu_;
   CefRefPtr<CefBrowserHostBase> browser_;
   CefRefPtr<CefContextMenuHandler> handler_;
@@ -186,6 +282,8 @@ class CefContextMenuObserver : public RenderViewContextMenuObserver,
   // Map of command_id to ItemInfo.
   using ItemInfoMap = std::map<int, ItemInfo>;
   ItemInfoMap iteminfomap_;
+
+  base::WeakPtrFactory<CefContextMenuObserver> weak_ptr_factory_{this};
 };
 
 std::unique_ptr<RenderViewContextMenuObserver> MenuCreatedCallback(
@@ -199,16 +297,44 @@ std::unique_ptr<RenderViewContextMenuObserver> MenuCreatedCallback(
                                                         handler);
       }
     }
+
+    // Don't leave the old pointer, if any.
+    browser->set_context_menu_observer(nullptr);
   }
 
   return nullptr;
 }
 
+bool MenuShowHandlerCallback(RenderViewContextMenu* context_menu) {
+  auto browser = CefBrowserHostBase::GetBrowserForContents(
+      context_menu->source_web_contents());
+  if (browser && browser->context_menu_observer()) {
+    return static_cast<CefContextMenuObserver*>(
+               browser->context_menu_observer())
+        ->HandleShow();
+  }
+  return false;
+}
+
 }  // namespace
 
-void RegisterMenuCreatedCallback() {
+void RegisterCallbacks() {
   RenderViewContextMenu::RegisterMenuCreatedCallback(
       base::BindRepeating(&MenuCreatedCallback));
+  RenderViewContextMenu::RegisterMenuShowHandlerCallback(
+      base::BindRepeating(&MenuShowHandlerCallback));
+}
+
+bool HandleContextMenu(content::WebContents* opener,
+                       const content::ContextMenuParams& params) {
+  auto browser = CefBrowserHostBase::GetBrowserForContents(opener);
+  if (browser && browser->IsAlloyStyle()) {
+    AlloyBrowserHostImpl::FromBaseChecked(browser)->ShowContextMenu(params);
+    return true;
+  }
+
+  // Continue with creating the RenderViewContextMenu.
+  return false;
 }
 
 }  // namespace context_menu