Reduce test.dart memory usage

tools/testing/dart/test_suite.dart

Index: tools/testing/dart/test_suite.dart
diff --git a/tools/testing/dart/test_suite.dart b/tools/testing/dart/test_suite.dart
index b3e216d70c901b8701a4c02cc869fcb214645796..07424155a08ea5652bd9594fc80e4fb0e36983d2 100644
--- a/tools/testing/dart/test_suite.dart
+++ b/tools/testing/dart/test_suite.dart
@@ -260,13 +260,8 @@ abstract class TestSuite {
     // Handle sharding based on the original test path (i.e. all multitests
     // of a given original test belong to the same shard)
     int shards = configuration['shards'];
-    if (shards > 1) {
-      int shard = configuration['shard'];
-      var testPath =
-          testCase.info.originTestPath.relativeTo(TestUtils.dartDir);
-      if ("$testPath".hashCode % shards != shard - 1) {
-        return;
-      }
+    if (shards > 1 && testCase.hash % shards != configuration['shard'] - 1) {
+      return;
     }
     // Test if the selector includes this test.
     RegExp pattern = configuration['selectors'][suiteName];
@@ -277,8 +272,7 @@ abstract class TestSuite {
     // Update Summary report
     if (configuration['report']) {
       SummaryReport.add(expectations);
-      if (testCase.info != null &&
-          testCase.expectCompileError &&
+      if (testCase.expectCompileError &&
           TestUtils.isBrowserRuntime(configuration['runtime']) &&
           new CompilerConfiguration(configuration).hasCompiler) {
         SummaryReport.addCompileErrorSkipTest();