Revert "Consistently use either "boot" or "apex" boot image as the default."

This reverts commit 48b3b3c71f76fa05de191b8460a186e9dbcc36bf.

Reason for revert: breaks emulator

BUG: 146558375

Change-Id: I2af3d11ad9a014b0d73a73540bc814f245bc6418
diff --git a/java/dexpreopt.go b/java/dexpreopt.go
index 1192d92..479dec6 100644
--- a/java/dexpreopt.go
+++ b/java/dexpreopt.go
@@ -101,6 +101,10 @@
 
 	global := dexpreoptGlobalConfig(ctx)
 	bootImage := defaultBootImageConfig(ctx)
+	defaultBootImage := bootImage
+	if global.UseApexImage {
+		bootImage = apexBootImageConfig(ctx)
+	}
 
 	var archs []android.ArchType
 	for _, a := range ctx.MultiTargets() {
@@ -170,8 +174,11 @@
 		DexPreoptImagesDeps:     imagesDeps,
 		DexPreoptImageLocations: bootImage.imageLocations,
 
-		PreoptBootClassPathDexFiles:     bootImage.dexPathsDeps.Paths(),
-		PreoptBootClassPathDexLocations: bootImage.dexLocationsDeps,
+		// We use the dex paths and dex locations of the default boot image, as it
+		// contains the full dexpreopt boot classpath. Other images may just contain a subset of
+		// the dexpreopt boot classpath.
+		PreoptBootClassPathDexFiles:     defaultBootImage.dexPathsDeps.Paths(),
+		PreoptBootClassPathDexLocations: defaultBootImage.dexLocationsDeps,
 
 		PreoptExtractedApk: false,