Ignore HasAlphaLayer flag to fix b/30929229

BUG:30929229
Change-Id: Iebadc6b3d224efa0554cbbb99ea43f871c28722b
diff --git a/libs/hwui/SkiaCanvas.cpp b/libs/hwui/SkiaCanvas.cpp
index ce67554..c7289fc 100644
--- a/libs/hwui/SkiaCanvas.cpp
+++ b/libs/hwui/SkiaCanvas.cpp
@@ -329,9 +329,10 @@
 static inline SkCanvas::SaveLayerFlags layerFlags(SaveFlags::Flags flags) {
     SkCanvas::SaveLayerFlags layerFlags = 0;
 
-    if (!(flags & SaveFlags::HasAlphaLayer)) {
-        layerFlags |= SkCanvas::kIsOpaque_SaveLayerFlag;
-    }
+    // We intentionally ignore the SaveFlags::HasAlphaLayer and
+    // SkCanvas::kIsOpaque_SaveLayerFlag flags because HWUI ignores it
+    // and our Android client may use it incorrectly.
+    // In Skia, this flag is purely for performance optimization.
 
     if (!(flags & SaveFlags::ClipToLayer)) {
         layerFlags |= SkCanvas::kDontClipToLayer_Legacy_SaveLayerFlag;