Fix a few typos in the front_end package.

pkg/front_end/lib/compiler_options.dart

 // Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library front_end.compiler_options;
 
 import 'compilation_error.dart';
 import 'file_system.dart';
 import 'physical_file_system.dart';
 
-/// Default error handler used by [CompielerOptions.onError].
+/// Default error handler used by [CompilerOptions.onError].
 void defaultErrorHandler(CompilationError error) => throw error;
 
 /// Callback used to report errors encountered during compilation.
 typedef void ErrorHandler(CompilationError error);
 
 /// Front-end options relevant to compiler back ends.
 ///
 /// Not intended to be implemented or extended by clients.
 class CompilerOptions {
   /// The URI of the root of the Dart SDK (typically a "file:" URI).
@@ skipping 83 matching lines @@
   ///
   /// This option is intended only for modular APIs like `kernelForBuildUnit`.
   /// These APIs by default ensure that builds are hermetic, where all files
   /// that will be compiled are listed explicitly and all other dependencies
   /// are covered by summary files.
   ///
   /// When this option is true, these APIs will treat any dependency that is
   /// not described in a summary as if it was explictly listed as an input.
   bool chaseDependencies = false;
 
-  /// Whether to intepret Dart sources in strong-mode.
+  /// Whether to interpret Dart sources in strong-mode.
   bool strongMode = true;
 
   // All options below are target-specific options.
   //
   // TODO(sigmund): revisit the right layout for these options. We might want to
   // split them out into a separate bag of options or provide factories for
   // common combinations of these options.
 
   /// Patch files to apply on the core libraries for a specific target platform.
   ///
   /// Keys on this map are expected to be `dart:*` URIs. The values can be
   /// either absolute or relative URIs. Absolute URIs are read directly, while
   /// relative URIs are resolved from the [sdkRoot].
   Map<Uri, List<Uri>> targetPatches = {};
 }