Revert "Get project list for guessing groups from in memory project cache"

This reverts commit 2bf8c1887f0381ddd1fd1b55c7352b981a2e4bf1.

Reason for revert: This made the latency for guessing groups worse
for us (Google). With this change the p99.9 latency increased by
~200ms. 

Change-Id: I496ec5c50e191f9f149c9eacda6e564831acf9ea
diff --git a/java/com/google/gerrit/server/project/ProjectCacheImpl.java b/java/com/google/gerrit/server/project/ProjectCacheImpl.java
index 0afaa3f..6498d1b 100644
--- a/java/com/google/gerrit/server/project/ProjectCacheImpl.java
+++ b/java/com/google/gerrit/server/project/ProjectCacheImpl.java
@@ -76,7 +76,6 @@
 import java.util.concurrent.ExecutionException;
 import java.util.concurrent.locks.Lock;
 import java.util.concurrent.locks.ReentrantLock;
-import java.util.stream.Stream;
 import org.eclipse.jgit.errors.ConfigInvalidException;
 import org.eclipse.jgit.errors.RepositoryNotFoundException;
 import org.eclipse.jgit.lib.Config;
@@ -301,20 +300,19 @@
   @Override
   public Set<AccountGroup.UUID> guessRelevantGroupUUIDs() {
     try (Timer0.Context ignored = guessRelevantGroupsLatency.start()) {
-      Stream<AccountGroup.UUID> configuredRelevantGroups =
-          Arrays.stream(config.getStringList("groups", /* subsection= */ null, "relevantGroup"))
-              .map(AccountGroup::uuid);
-
-      Stream<AccountGroup.UUID> guessedRelevantGroups =
-          inMemoryProjectCache.asMap().values().stream()
-              .filter(Objects::nonNull)
-              .flatMap(p -> p.getAllGroupUUIDs().stream())
-              // getAllGroupUUIDs shouldn't really return null UUIDs, but harden
-              // against them just in case there is a bug or corner case.
-              .filter(id -> id != null && id.get() != null);
-
       Set<AccountGroup.UUID> relevantGroupUuids =
-          Streams.concat(configuredRelevantGroups, guessedRelevantGroups).collect(toSet());
+          Streams.concat(
+                  Arrays.stream(
+                          config.getStringList("groups", /* subsection= */ null, "relevantGroup"))
+                      .map(AccountGroup::uuid),
+                  all().stream()
+                      .map(n -> inMemoryProjectCache.getIfPresent(n))
+                      .filter(Objects::nonNull)
+                      .flatMap(p -> p.getAllGroupUUIDs().stream())
+                      // getAllGroupUUIDs shouldn't really return null UUIDs, but harden
+                      // against them just in case there is a bug or corner case.
+                      .filter(id -> id != null && id.get() != null))
+              .collect(toSet());
       logger.atFine().log("relevant group UUIDs: %s", relevantGroupUuids);
       return relevantGroupUuids;
     }