Implement external stencil for Android WebView

android_webview/browser/parent_output_surface.h

Index: android_webview/browser/parent_output_surface.h
diff --git a/android_webview/browser/parent_output_surface.h b/android_webview/browser/parent_output_surface.h
index 0467f2ace6ae3076dd4b346c61ea71ffa96d83ad..f69598e17ae41daba65c230b8a565b23ab9f9f3e 100644
--- a/android_webview/browser/parent_output_surface.h
+++ b/android_webview/browser/parent_output_surface.h
@@ -5,6 +5,7 @@
 #ifndef ANDROID_WEBVIEW_BROWSER_PARENT_OUTPUT_SURFACE_H_
 #define ANDROID_WEBVIEW_BROWSER_PARENT_OUTPUT_SURFACE_H_
 
+#include "android_webview/browser/scoped_app_gl_state_restore.h"
 #include "base/macros.h"
 #include "cc/output/output_surface.h"
 
@@ -22,9 +23,13 @@ class ParentOutputSurface : NON_EXPORTED_BASE(public cc::OutputSurface) {
                float scale_factor,
                bool has_alpha) override;
   void SwapBuffers(cc::CompositorFrame* frame) override;
-  using cc::OutputSurface::SetExternalStencilTest;
+  void ApplyExternalStencil() override;
+
+  void SetGLState(const ScopedAppGLStateRestore& gl_state);
 
  private:
+  StencilState stencil_state_;
+
   DISALLOW_COPY_AND_ASSIGN(ParentOutputSurface);
 };