HWC2: Kill logspam for non-HWC virtual displays

Removes some logspam and fixes some non-errors which were reported as
errors when running a virtual display that is not backed by hardware
composer.

Bug: 30022738
Change-Id: Ie966e37d95f53bcc050eef064d24bbe26748b7fd
diff --git a/services/surfaceflinger/Layer.cpp b/services/surfaceflinger/Layer.cpp
index 30a4d79..4d04072 100644
--- a/services/surfaceflinger/Layer.cpp
+++ b/services/surfaceflinger/Layer.cpp
@@ -1058,8 +1058,13 @@
 }
 
 HWC2::Composition Layer::getCompositionType(int32_t hwcId) const {
+    if (hwcId == DisplayDevice::DISPLAY_ID_INVALID) {
+        // If we're querying the composition type for a display that does not
+        // have a HWC counterpart, then it will always be Client
+        return HWC2::Composition::Client;
+    }
     if (mHwcLayers.count(hwcId) == 0) {
-        ALOGE("getCompositionType called without a valid HWC layer");
+        ALOGE("getCompositionType called with an invalid HWC layer");
         return HWC2::Composition::Invalid;
     }
     return mHwcLayers.at(hwcId).compositionType;