Do not run unnecessary code in the common case

`processes` is initialized as an empty map, so we're currently always
hitting the loop case. We should avoid it.

Bug: 213021110
Test: atest PackageManagerPerfTest#testGetApplicationInfoWithFiltering
Test: atest CtsProcessTest
Test: atest PackageManagerServiceUnitTests
Change-Id: I49fa8adb0cf10e405b2251e7de78caea1bbd8fa1

core/java/android/content/pm/parsing/ParsingPackageImpl.java

@@ -1152,7 +1152,7 @@ public class ParsingPackageImpl implements ParsingPackage, ParsingPackageHidden,
      */
     @Nullable
     private ArrayMap<String, String> buildAppClassNamesByProcess() {
-        if (processes == null) {
+        if (ArrayUtils.size(processes) == 0) {
             return null;
         }
         final ArrayMap<String, String> ret = new ArrayMap<>(4);