[ComposerService] Add API to query protected content support.

Add API to query protected content support for upper stack usage.

BUG: 117436546
Test: Build, flash and boot. Check returned value.
Change-Id: I1bc7320a2ce5a99889c979f6d6fd159369668871
diff --git a/services/surfaceflinger/SurfaceFlinger.h b/services/surfaceflinger/SurfaceFlinger.h
index 134f9c2..460f041 100644
--- a/services/surfaceflinger/SurfaceFlinger.h
+++ b/services/surfaceflinger/SurfaceFlinger.h
@@ -457,6 +457,7 @@
     status_t getDisplayedContentSample(const sp<IBinder>& display, uint64_t maxFrames,
                                        uint64_t timestamp,
                                        DisplayedFrameStats* outStats) const override;
+    status_t getProtectedContentSupport(bool* outSupported) const override;
 
     /* ------------------------------------------------------------------------
      * DeathRecipient interface