Don't fill boundary rectangle when drawing shadows.

SurfaceFlinger splits up EffectLayers containing shadows into multiple
parts:
1. A layer only containing the shadow metadata, and
2. Either a background blur or a solid color.

Since the default solid color is an opaque black, this causes shadows to
black out PIP windows.

A follow-up patch should change the default solid color to be a
transparent black instead so that nothing is drawn, or define a
canonical invalid color but we'd have to check callers to make sure
the GLES path doesn't break either.

Bug: 175824511
Bug: 175819287
Test: PIP window
Change-Id: I21336a7885299a127f3dad2a6b88c9dcab0b5980
diff --git a/services/surfaceflinger/Layer.cpp b/services/surfaceflinger/Layer.cpp
index 0e861ab..9237113 100644
--- a/services/surfaceflinger/Layer.cpp
+++ b/services/surfaceflinger/Layer.cpp
@@ -688,6 +688,7 @@
     shadowLayer.source.buffer.fence = nullptr;
     shadowLayer.frameNumber = 0;
     shadowLayer.bufferId = 0;
+    shadowLayer.name = getName();
 
     if (shadowLayer.shadow.ambientColor.a <= 0.f && shadowLayer.shadow.spotColor.a <= 0.f) {
         return {};
@@ -723,6 +724,7 @@
 
     // If layer is blacked out, force alpha to 1 so that we draw a black color layer.
     layerSettings.alpha = blackout ? 1.0f : 0.0f;
+    layerSettings.name = getName();
 }
 
 std::vector<compositionengine::LayerFE::LayerSettings> Layer::prepareClientCompositionList(