SF: Add support for screen captures

Add Layer::drawNow to support capturing portions
of the screen in the FE, as this is not tied
to vsync

Test: Compile/Run manually
Merged-Id: I0781d44240ae127a6e70b35282a02cbedfe36fe4
Change-Id: I0781d44240ae127a6e70b35282a02cbedfe36fe4
diff --git a/services/surfaceflinger/BufferLayer.h b/services/surfaceflinger/BufferLayer.h
index 6b02f8c..c7b09ad 100644
--- a/services/surfaceflinger/BufferLayer.h
+++ b/services/surfaceflinger/BufferLayer.h
@@ -101,6 +101,7 @@
      */
     void onDraw(const RenderArea& renderArea, const Region& clip,
                 bool useIdentityTransform) const override;
+    void drawNow(const RenderArea& renderArea, bool useIdentityTransform) const;
 
     void onLayerDisplayed(const sp<Fence>& releaseFence) override;