Move Alloy-specific logic to CefBrowserPlatformDelegateAlloy (see issue #2969)

Also remove OSR-related methods where the attributes can instead be passed
to the OSR platform delegate constructor directly.

libcef/browser/osr/browser_platform_delegate_osr_win.h

@@ -11,7 +11,9 @@
 class CefBrowserPlatformDelegateOsrWin : public CefBrowserPlatformDelegateOsr {
  public:
   explicit CefBrowserPlatformDelegateOsrWin(
-      std::unique_ptr<CefBrowserPlatformDelegateNative> native_delegate);
+      std::unique_ptr<CefBrowserPlatformDelegateNative> native_delegate,
+      bool use_shared_texture,
+      bool use_external_begin_frame);
 
   // CefBrowserPlatformDelegate methods:
   CefWindowHandle GetHostWindowHandle() const override;