Revert "Revert "[SurfaceFlinger] Add GPU protected content support.""

This reverts commit 78fb96f3f8b40cba6b9e2cb2b0c332a45798b522.
Reason for revert: Revert the revert with Fix.

BUG: 35315015
Test: Test with a hacked patch.
Test: Watch Youtube movie, verifed by force GPU composition.
Change-Id: Ic738b5f873dbff322473d4f999074dc35c8813c7
diff --git a/libs/renderengine/gl/GLImage.h b/libs/renderengine/gl/GLImage.h
index c897d8e..59d6ce3 100644
--- a/libs/renderengine/gl/GLImage.h
+++ b/libs/renderengine/gl/GLImage.h
@@ -39,10 +39,12 @@
     bool setNativeWindowBuffer(ANativeWindowBuffer* buffer, bool isProtected) override;
 
     EGLImageKHR getEGLImage() const { return mEGLImage; }
+    bool isProtected() const { return mProtected; }
 
 private:
     EGLDisplay mEGLDisplay;
     EGLImageKHR mEGLImage = EGL_NO_IMAGE_KHR;
+    bool mProtected = false;
 
     DISALLOW_COPY_AND_ASSIGN(GLImage);
 };