Keep main dex check enabled in D8

RELNOTES: Building Android apps for legacy multi-dex (pre-L) now require a main-dex list if the application does not fit into a single DEX file.
PiperOrigin-RevId: 327633282

src/tools/android/java/com/android/tools/r8/CompatDxSupport.java

diff --git a/src/tools/android/java/com/android/tools/r8/CompatDxSupport.java b/src/tools/android/java/com/android/tools/r8/CompatDxSupport.java
index 68aaf8a..70d1c0e 100644
--- a/src/tools/android/java/com/android/tools/r8/CompatDxSupport.java
+++ b/src/tools/android/java/com/android/tools/r8/CompatDxSupport.java
@@ -13,7 +13,6 @@
 // limitations under the License.
 package com.android.tools.r8;
 
-import java.lang.reflect.Field;
 import java.lang.reflect.Method;
 
 /**
@@ -58,23 +57,6 @@
       // as bazel might link to a shrunken r8.jar which does not have these APIs.
       Object app = getInputAppMethod.invoke(command);
       Object options = getInternalOptionsMethod.invoke(command);
-      // DX allows --multi-dex without specifying a main dex list for legacy devices.
-      // That is broken, but for CompatDX we do the same to not break existing builds
-      // that are trying to transition.
-      try {
-        Field enableMainDexListCheckField = internalOptionsClass.getField("enableMainDexListCheck");
-        try {
-          // Use reflection for:
-          //   <code>options.enableMainDexListCheck = false;</code>
-          // as bazel might link to an old r8.jar which does not have this field.
-          enableMainDexListCheckField.setBoolean(options, false);
-        } catch (IllegalAccessException e) {
-          throw new AssertionError("Unsupported r8.jar", e);
-        }
-      } catch (NoSuchFieldException e) {
-        // Ignore if bazel is linking to an old r8.jar.
-      }
-
       runForTestingMethod.invoke(null, app, options);
     } catch (ReflectiveOperationException e) {
       // This is an unsupported r8.jar.

src/tools/android/java/com/google/devtools/build/android/r8/CompatDx.java

diff --git a/src/tools/android/java/com/google/devtools/build/android/r8/CompatDx.java b/src/tools/android/java/com/google/devtools/build/android/r8/CompatDx.java
index d7cddd5..5e1afdf 100644
--- a/src/tools/android/java/com/google/devtools/build/android/r8/CompatDx.java
+++ b/src/tools/android/java/com/google/devtools/build/android/r8/CompatDx.java
@@ -46,7 +46,6 @@
 import java.io.InputStream;
 import java.io.OutputStream;
 import java.io.PrintStream;
-import java.lang.reflect.Method;
 import java.nio.file.Files;
 import java.nio.file.Path;
 import java.nio.file.Paths;
@@ -637,19 +636,7 @@
       if (dexArgs.backportStatics) {
         CompatDxSupport.enableDesugarBackportStatics(builder);
       }
-      try {
-        // Check if the referenced r8.jar has these methods. If so, the support code accessing
-        // the internals is not required.
-        Method setEnableMainDexListCheck =
-            D8Command.Builder.class.getDeclaredMethod("setEnableMainDexListCheck", boolean.class);
-        // The methods are package private to not reveal them as part of the external API.
-        setEnableMainDexListCheck.setAccessible(true);
-        setEnableMainDexListCheck.invoke(builder, Boolean.FALSE);
-        D8.run(builder.build());
-      } catch (ReflectiveOperationException e) {
-        // Go through the support code accessing the internals for the compilation.
-        CompatDxSupport.run(builder.build());
-      }
+      D8.run(builder.build());
     } finally {
       executor.shutdown();
     }