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.

patch/patches/compositor_1368.patch

@@ -1,76 +0,0 @@
-diff --git content/browser/compositor/gpu_process_transport_factory.cc content/browser/compositor/gpu_process_transport_factory.cc
-index 642fff3b4367..45faeed249c0 100644
---- content/browser/compositor/gpu_process_transport_factory.cc
-+++ content/browser/compositor/gpu_process_transport_factory.cc
-@@ -493,10 +493,20 @@ void GpuProcessTransportFactory::EstablishedGpuChannel(
-         // surfaces as they are not following the correct mode.
-         DisableGpuCompositing(compositor.get());
-       }
-+
-+      std::unique_ptr<viz::SoftwareOutputDevice> output_device;
-+      if (compositor->delegate()) {
-+        output_device = compositor->delegate()->CreateSoftwareOutputDevice(
-+            compositor.get());
-+      }
-+      if (!output_device) {
-+        output_device = CreateSoftwareOutputDevice(compositor->widget(),
-+                                                   compositor->task_runner());
-+      }
-+
-       display_output_surface =
-           std::make_unique<SoftwareBrowserCompositorOutputSurface>(
--              CreateSoftwareOutputDevice(compositor->widget(),
--                                         compositor->task_runner()),
-+              std::move(output_device),
-               std::move(vsync_callback));
-     } else {
-       DCHECK(context_provider);
-diff --git ui/compositor/compositor.h ui/compositor/compositor.h
-index a974ea654834..cfb3ff7f8a0c 100644
---- ui/compositor/compositor.h
-+++ ui/compositor/compositor.h
-@@ -25,6 +25,7 @@
- #include "components/viz/common/surfaces/frame_sink_id.h"
- #include "components/viz/common/surfaces/local_surface_id.h"
- #include "components/viz/host/host_frame_sink_client.h"
-+#include "components/viz/service/display/software_output_device.h"
- #include "third_party/skia/include/core/SkColor.h"
- #include "third_party/skia/include/core/SkMatrix44.h"
- #include "ui/compositor/compositor_animation_observer.h"
-@@ -200,6 +201,17 @@ class COMPOSITOR_EXPORT ContextFactory {
-   virtual bool SyncTokensRequiredForDisplayCompositor() = 0;
- };
- 
-+class COMPOSITOR_EXPORT CompositorDelegate {
-+ public:
-+  virtual std::unique_ptr<viz::SoftwareOutputDevice> CreateSoftwareOutputDevice(
-+      ui::Compositor* compositor) {
-+    return nullptr;
-+  }
-+
-+ protected:
-+  virtual ~CompositorDelegate() {}
-+};
-+
- // Compositor object to take care of GPU painting.
- // A Browser compositor object is responsible for generating the final
- // displayable form of pixels comprising a single widget's contents. It draws an
-@@ -240,6 +252,9 @@ class COMPOSITOR_EXPORT Compositor : public cc::LayerTreeHostClient,
-   // Schedules a redraw of the layer tree associated with this compositor.
-   void ScheduleDraw();
- 
-+  CompositorDelegate* delegate() const { return delegate_; }
-+  void SetDelegate(CompositorDelegate* delegate) { delegate_ = delegate; }
-+
-   // Sets the root of the layer tree drawn by this Compositor. The root layer
-   // must have no parent. The compositor's root layer is reset if the root layer
-   // is destroyed. NULL can be passed to reset the root layer, in which case the
-@@ -463,6 +478,8 @@ class COMPOSITOR_EXPORT Compositor : public cc::LayerTreeHostClient,
-   ui::ContextFactory* context_factory_;
-   ui::ContextFactoryPrivate* context_factory_private_;
- 
-+  CompositorDelegate* delegate_ = nullptr;
-+
-   // The root of the Layer tree drawn by this compositor.
-   Layer* root_layer_ = nullptr;
-