PointerIcon: Treat 0 as a valid type index for system icons

PointerIcon.TYPE_ALIAS maps to the style type index of 0, which we
incorrectly treat as "invalid" in the code. This means we can never load
the TYPE_ALIAS system icon correctly.

Fix this by using an index of -1 to represent an invalid index.

Fixes: 339233006
Test: presubmit
Change-Id: I28cb4ce53dafa9de88959ba425889fec42d1e722
diff --git a/core/java/android/view/PointerIcon.java b/core/java/android/view/PointerIcon.java
index 7dc151d..71199e9 100644
--- a/core/java/android/view/PointerIcon.java
+++ b/core/java/android/view/PointerIcon.java
@@ -234,7 +234,7 @@
         }
 
         int typeIndex = getSystemIconTypeIndex(type);
-        if (typeIndex == 0) {
+        if (typeIndex < 0) {
             typeIndex = getSystemIconTypeIndex(TYPE_DEFAULT);
         }
 
@@ -606,7 +606,7 @@
             case TYPE_HANDWRITING:
                 return com.android.internal.R.styleable.Pointer_pointerIconHandwriting;
             default:
-                return 0;
+                return -1;
         }
     }