Plumb HDR capabilities up to SurfaceComposerClient

Plumbs HDR capabilities up from HWC2 through SurfaceFlinger and
ISurfaceComposer to SurfaceComposerClient.

Bug: 25684127
Change-Id: I0f07043ff42bfc7a159f785fee3e84936dc3c280
diff --git a/services/surfaceflinger/SurfaceFlinger.h b/services/surfaceflinger/SurfaceFlinger.h
index 37110b9..8c974d0 100644
--- a/services/surfaceflinger/SurfaceFlinger.h
+++ b/services/surfaceflinger/SurfaceFlinger.h
@@ -222,6 +222,8 @@
     virtual status_t setActiveConfig(const sp<IBinder>& display, int id);
     virtual status_t clearAnimationFrameStats();
     virtual status_t getAnimationFrameStats(FrameStats* outStats) const;
+    virtual status_t getHdrCapabilities(const sp<IBinder>& display,
+            HdrCapabilities* outCapabilities) const;
 
     /* ------------------------------------------------------------------------
      * DeathRecipient interface