Adding Angular and dependent packages for testing

third_party/pkg/angular/lib/mock/exception_handler.dart

+part of angular.mock;
+
+/**
+ * Mock implementation of [ExceptionHandler] that rethrows exceptions.
+ */
+class RethrowExceptionHandler extends ExceptionHandler {
+  call(error, stack, [reason]){
+    throw "$error $reason \nORIGINAL STACKTRACE:\n $stack";
+  }
+}
+
+class ExceptionWithStack {
+  final dynamic error;
+  final dynamic stack;
+  ExceptionWithStack(this.error, this.stack);
+  toString() => "$error\n$stack";
+}
+
+/**
+ * Mock implementation of [ExceptionHandler] that logs all exceptions for
+ * later processing.
+ */
+class LoggingExceptionHandler implements ExceptionHandler {
+  /**
+   * All exceptions are stored here for later examining.
+   */
+  final List<ExceptionWithStack> errors = [];
+
+  call(error, stack, [reason]) {
+    errors.add(new ExceptionWithStack(error, stack));
+  }
+
+  /**
+   * This method throws an exception if the errors is not empty.
+   * It is recommended that this method is called on test tear-down
+   * to verify that all exceptions have been processed.
+   */
+  assertEmpty() {
+    if (errors.length > 0) {
+      throw new ArgumentError('Exception Logger not empty:\n$errors');
+    }
+  }
+}