More WebView HDR plumbing

Pass through format for GL
and shouldDither if HWUI wants
dithering globally enabled

Fixes: 279030860
Test: make
Change-Id: Ic9e767fede8be9664bb87a340573e5f424d0de3e
diff --git a/libs/hwui/renderthread/CanvasContext.h b/libs/hwui/renderthread/CanvasContext.h
index d7215de..613381a 100644
--- a/libs/hwui/renderthread/CanvasContext.h
+++ b/libs/hwui/renderthread/CanvasContext.h
@@ -234,6 +234,8 @@
 
     void startHintSession();
 
+    static bool shouldDither();
+
 private:
     CanvasContext(RenderThread& thread, bool translucent, RenderNode* rootRenderNode,
                   IContextFactory* contextFactory, std::unique_ptr<IRenderPipeline> renderPipeline,