Change the assumption that there's always at least one ambient layer

At Samsung's request, remove the logic that assumed there is always
at least one layer needed for ambient memory calculations.

play-validations/memory-footprint/src/main/java/com/google/wear/watchface/dfx/memory/AmbientMemoryFootprintCalculator.java

@@ -118,11 +118,6 @@ long computeAmbientMemoryFootprint(long screenWidth, long screenHeight) {
                 perConfigurationDynamicResources.computeMaximumResourceUsage(
                         visitor.optionResources);
 
-        // There's always at least one layer, even if all the Part* nodes are hidden.
-        if (visitor.numLayers == 0) {
-            visitor.numLayers = 1;
-        }
-
         // In V1 we support a maximum of 2 layers and 2 clocks.
         if (evaluationSettings.applyV1OffloadLimitations()) {
             visitor.numLayers = min(visitor.numLayers, 2);