Add support for loading extensions (issue #1947)

- Add CefRequestContext::LoadExtension, CefExtension, CefExtensionHandler and
  related methods/interfaces.
- Add chrome://extensions-support that lists supported Chrome APIs.
- Add CefBrowserHost::SetAutoResizeEnabled and CefDisplayHandler::OnAutoResize
  to support browser resize based on preferred web contents size.
- views: Add support for custom CefMenuButton popups.
- cefclient: Run with `--load-extension=set_page_color` command-line flag for
  an extension loading example. Add `--use-views` on Windows and Linux for an
  even better example.

libcef/browser/extensions/browser_platform_delegate_background.cc

@@ -0,0 +1,153 @@
+// Copyright 2017 The Chromium Embedded Framework Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "libcef/browser/extensions/browser_platform_delegate_background.h"
+
+#include <utility>
+
+#include "libcef/browser/browser_host_impl.h"
+#include "libcef/browser/thread_util.h"
+
+#include "content/public/browser/render_view_host.h"
+#include "content/public/browser/render_widget_host.h"
+
+CefBrowserPlatformDelegateBackground::CefBrowserPlatformDelegateBackground(
+    std::unique_ptr<CefBrowserPlatformDelegateNative> native_delegate)
+    : native_delegate_(std::move(native_delegate)) {
+  native_delegate_->set_windowless_handler(this);
+}
+
+bool CefBrowserPlatformDelegateBackground::CreateHostWindow() {
+  // Nothing to do here.
+  return true;
+}
+
+void CefBrowserPlatformDelegateBackground::CloseHostWindow() {
+  // No host window, so continue browser destruction now. Do it asynchronously
+  // so the call stack has a chance to unwind.
+  CEF_POST_TASK(CEF_UIT,
+                base::Bind(&CefBrowserHostImpl::WindowDestroyed, browser_));
+}
+
+CefWindowHandle CefBrowserPlatformDelegateBackground::GetHostWindowHandle()
+    const {
+  return kNullWindowHandle;
+}
+
+SkColor CefBrowserPlatformDelegateBackground::GetBackgroundColor() const {
+  return native_delegate_->GetBackgroundColor();
+}
+
+void CefBrowserPlatformDelegateBackground::WasResized() {
+  // Nothing to do here.
+}
+
+void CefBrowserPlatformDelegateBackground::SendKeyEvent(
+    const content::NativeWebKeyboardEvent& event) {
+  // Nothing to do here.
+}
+
+void CefBrowserPlatformDelegateBackground::SendMouseEvent(
+    const blink::WebMouseEvent& event) {
+  // Nothing to do here.
+}
+
+void CefBrowserPlatformDelegateBackground::SendMouseWheelEvent(
+    const blink::WebMouseWheelEvent& event) {
+  // Nothing to do here.
+}
+
+void CefBrowserPlatformDelegateBackground::SendFocusEvent(bool setFocus) {
+  // Nothing to do here.
+}
+
+gfx::Point CefBrowserPlatformDelegateBackground::GetScreenPoint(
+    const gfx::Point& view_pt) const {
+  // Nothing to do here.
+  return view_pt;
+}
+
+void CefBrowserPlatformDelegateBackground::ViewText(const std::string& text) {
+  native_delegate_->ViewText(text);
+}
+
+void CefBrowserPlatformDelegateBackground::HandleKeyboardEvent(
+    const content::NativeWebKeyboardEvent& event) {
+  // Nothing to do here.
+}
+
+void CefBrowserPlatformDelegateBackground::HandleExternalProtocol(
+    const GURL& url) {
+  native_delegate_->HandleExternalProtocol(url);
+}
+
+void CefBrowserPlatformDelegateBackground::TranslateKeyEvent(
+    content::NativeWebKeyboardEvent& result,
+    const CefKeyEvent& key_event) const {
+  native_delegate_->TranslateKeyEvent(result, key_event);
+}
+
+void CefBrowserPlatformDelegateBackground::TranslateClickEvent(
+    blink::WebMouseEvent& result,
+    const CefMouseEvent& mouse_event,
+    CefBrowserHost::MouseButtonType type,
+    bool mouseUp,
+    int clickCount) const {
+  native_delegate_->TranslateClickEvent(result, mouse_event, type, mouseUp,
+                                        clickCount);
+}
+
+void CefBrowserPlatformDelegateBackground::TranslateMoveEvent(
+    blink::WebMouseEvent& result,
+    const CefMouseEvent& mouse_event,
+    bool mouseLeave) const {
+  native_delegate_->TranslateMoveEvent(result, mouse_event, mouseLeave);
+}
+
+void CefBrowserPlatformDelegateBackground::TranslateWheelEvent(
+    blink::WebMouseWheelEvent& result,
+    const CefMouseEvent& mouse_event,
+    int deltaX,
+    int deltaY) const {
+  native_delegate_->TranslateWheelEvent(result, mouse_event, deltaX, deltaY);
+}
+
+CefEventHandle CefBrowserPlatformDelegateBackground::GetEventHandle(
+    const content::NativeWebKeyboardEvent& event) const {
+  return native_delegate_->GetEventHandle(event);
+}
+
+std::unique_ptr<CefFileDialogRunner>
+CefBrowserPlatformDelegateBackground::CreateFileDialogRunner() {
+  return native_delegate_->CreateFileDialogRunner();
+}
+
+std::unique_ptr<CefJavaScriptDialogRunner>
+CefBrowserPlatformDelegateBackground::CreateJavaScriptDialogRunner() {
+  return native_delegate_->CreateJavaScriptDialogRunner();
+}
+
+std::unique_ptr<CefMenuRunner>
+CefBrowserPlatformDelegateBackground::CreateMenuRunner() {
+  // No default menu implementation for background browsers.
+  return nullptr;
+}
+
+bool CefBrowserPlatformDelegateBackground::IsWindowless() const {
+  return false;
+}
+
+bool CefBrowserPlatformDelegateBackground::IsViewsHosted() const {
+  return false;
+}
+
+CefWindowHandle CefBrowserPlatformDelegateBackground::GetParentWindowHandle()
+    const {
+  return GetHostWindowHandle();
+}
+
+gfx::Point CefBrowserPlatformDelegateBackground::GetParentScreenPoint(
+    const gfx::Point& view) const {
+  return GetScreenPoint(view);
+}