Do not compile tests for different browsers separately

tools/testing/dart/test_runner.dart

Index: tools/testing/dart/test_runner.dart
diff --git a/tools/testing/dart/test_runner.dart b/tools/testing/dart/test_runner.dart
index 73c9cba04c25affcc6683ff3a7c55354d7866597..012f1daf5eed9d8f2476eafd5ae75c8f173354e2 100644
--- a/tools/testing/dart/test_runner.dart
+++ b/tools/testing/dart/test_runner.dart
@@ -123,6 +123,8 @@ class Command {
 
   String toString() => commandLine;
 
+  Future postProcessCommand() => new Future.immediate(null);
+
   Future<bool> get outputIsUpToDate => new Future.immediate(false);
   io.Path get expectedOutputFile => null;
   bool get isPixelTest => false;
@@ -130,10 +132,12 @@ class Command {
 
 class CompilationCommand extends Command {
   String _outputFile;
+  String _shadowFile;
   bool _neverSkipCompilation;
   List<Uri> _bootstrapDependencies;
 
   CompilationCommand(this._outputFile,
+                     this._shadowFile,
                      this._neverSkipCompilation,
                      this._bootstrapDependencies,
                      String executable,
@@ -160,11 +164,11 @@ class CompilationCommand extends Command {
       });
     }
 
-    return readDepsFile("$_outputFile.deps").then((dependencies) {
+    return readDepsFile("${_shadowFile}.deps").then((dependencies) {
       if (dependencies != null) {
         dependencies.addAll(_bootstrapDependencies);
         var jsOutputLastModified = TestUtils.lastModifiedCache.getLastModified(
-            new Uri.fromComponents(scheme: 'file', path: _outputFile));
+            new Uri.fromComponents(scheme: 'file', path: _shadowFile));
         if (jsOutputLastModified != null) {
           for (var dependency in dependencies) {
             var dependencyLastModified =
@@ -174,12 +178,33 @@ class CompilationCommand extends Command {
               return false;
             }
           }
+          // Shadow files are up to date, so copy them.
+          _copyFilesSync(_shadowFile, _outputFile);
           return true;
         }
       }
       return false;
     });
   }
+
+  Future postProcessCommand() {
+    // After the actual compile, we synchronously copy the compiled output files
+    // to shadow files.
+    _copyFilesSync(_outputFile, _shadowFile);
+    return new Future.immediate(null);
+  }
+
+  _copyFilesSync(String from, String to) {
+    for (var ending in ['', '.deps', '.map']) {
+      var fromFile = new io.File("${from}${ending}");
+      var toFile = new io.File("${to}${ending}");
+      // We copy the dart2js results synchronously to make it atomic.
+      // This ensures that the shadow files are always in a consistent state (no
+      // other code in the testing scripts will see a half-written shadow
+      // file).
+      toFile.writeAsBytesSync(fromFile.readAsBytesSync());
+    }
+  }
 }
 
 class ContentShellCommand extends Command {
@@ -1044,7 +1069,15 @@ class RunningProcess {
               process.kill();
             }
           }
-          process.exitCode.then(_commandComplete);
+          process.exitCode.then((exitCode) {
+            if (exitCode == 0) {
+              command.postProcessCommand().then((_) {
+                _commandComplete(exitCode);
+              });
+            } else {
+              _commandComplete(exitCode);
+            }
+          });
           _drainStream(process.stdout, stdout);
           _drainStream(process.stderr, stderr);
           timeoutTimer = new Timer(new Duration(seconds: testCase.timeout),