[benchmarks] Report VM platform file sizes under their old names for continuity of benchmarking data.

Cf. ab4f935

Change-Id: Iac3773c953c59d0a9ec60f069866a97499bc0494
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/435280
Commit-Queue: Ryan Macnak <[email protected]>
Reviewed-by: Alexander Aprelev <[email protected]>

Author: rmacnak-google

benchmarks/SDKArtifactSizes/dart/SDKArtifactSizes.dart

@@ -62,11 +62,15 @@ void main() {
     reportFileSize(executablePath, executable);
   }
 
-  for (final lib in libs) {
-    final libPath = '$rootDir/dart-sdk/lib/_internal/$lib';
-    reportFileSize(libPath, lib);
+  void reportLib(String lib, String name) {
+    reportFileSize('$rootDir/dart-sdk/lib/_internal/$lib', name);
   }
 
+  // Continue reporting the file size under the old name for continuity of
+  // benchmarking data.
+  reportLib('vm_platform.dill', 'vm_platform_strong.dill');
+  reportLib('vm_platform_product.dill', 'vm_platform_strong_product.dill');
+
   for (final snapshot in snapshots) {
     final snapshotPath =
         '$rootDir/dart-sdk/bin/snapshots/$snapshot.dart.snapshot';