Add support for shared texture and external BeginFrame in OSR mode (issue #1006)

- Add CefWindowInfo::shared_texture_enabled and
  CefRenderHandler::OnAcceleratedPaint for shared texture support. Currently
  only supported on Windows (D3D11).
- Add CefWindowInfo::external_begin_frame_enabled and
  CefBrowserHost::SendExternalBeginFrame for external begin frame support.

libcef/browser/extensions/browser_platform_delegate_background.cc

@@ -35,6 +35,14 @@ CefWindowHandle CefBrowserPlatformDelegateBackground::GetHostWindowHandle()
   return kNullWindowHandle;
 }
 
+bool CefBrowserPlatformDelegateBackground::CanUseSharedTexture() const {
+  return native_delegate_->CanUseSharedTexture();
+}
+
+bool CefBrowserPlatformDelegateBackground::CanUseExternalBeginFrame() const {
+  return native_delegate_->CanUseExternalBeginFrame();
+}
+
 SkColor CefBrowserPlatformDelegateBackground::GetBackgroundColor() const {
   return native_delegate_->GetBackgroundColor();
 }

libcef/browser/extensions/browser_platform_delegate_background.h

@@ -22,6 +22,8 @@ class CefBrowserPlatformDelegateBackground
   void CloseHostWindow() override;
   CefWindowHandle GetHostWindowHandle() const override;
   SkColor GetBackgroundColor() const override;
+  bool CanUseSharedTexture() const override;
+  bool CanUseExternalBeginFrame() const override;
   void SynchronizeVisualProperties() override;
   void SendKeyEvent(const content::NativeWebKeyboardEvent& event) override;
   void SendMouseEvent(const blink::WebMouseEvent& event) override;

libcef/browser/extensions/mime_handler_view_guest_delegate.cc

@@ -42,8 +42,8 @@ void CefMimeHandlerViewGuestDelegate::OverrideWebContentsCreateParams(
 
   CefRefPtr<CefBrowserHostImpl> owner_browser = GetOwnerBrowser(guest_);
   if (owner_browser->IsWindowless()) {
-    CefWebContentsViewOSR* view_osr =
-        new CefWebContentsViewOSR(owner_browser->GetBackgroundColor());
+    CefWebContentsViewOSR* view_osr = new CefWebContentsViewOSR(
+        owner_browser->GetBackgroundColor(), false, false);
     params->view = view_osr;
     params->delegate_view = view_osr;
   }