[SurfaceFlinger] Add GPU protected content support.

BUG: 35315015
Test: Test with a hacked patch.
Test: Watch Youtube movie, verifed by force GPU composition.
Change-Id: I1130c3ce7b534bfc1efefdf5a70b23311e2de944
diff --git a/services/surfaceflinger/SurfaceFlinger.cpp b/services/surfaceflinger/SurfaceFlinger.cpp
index a142928..a0102a5 100644
--- a/services/surfaceflinger/SurfaceFlinger.cpp
+++ b/services/surfaceflinger/SurfaceFlinger.cpp
@@ -5483,10 +5483,11 @@
         ALOGW("FB is protected: PERMISSION_DENIED");
         return PERMISSION_DENIED;
     }
+    auto& engine(getRenderEngine());
 
     // this binds the given EGLImage as a framebuffer for the
     // duration of this scope.
-    renderengine::BindNativeBufferAsFramebuffer bufferBond(getRenderEngine(), buffer);
+    renderengine::BindNativeBufferAsFramebuffer bufferBond(engine, buffer);
     if (bufferBond.getStatus() != NO_ERROR) {
         ALOGE("got ANWB binding error while taking screenshot");
         return INVALID_OPERATION;
@@ -5498,9 +5499,9 @@
     // dependent on the context's EGLConfig.
     renderScreenImplLocked(renderArea, traverseLayers, useIdentityTransform);
 
-    base::unique_fd syncFd = getRenderEngine().flush();
+    base::unique_fd syncFd = engine.flush();
     if (syncFd < 0) {
-        getRenderEngine().finish();
+        engine.finish();
     }
     *outSyncFd = syncFd.release();