Add a fallback mode for building summaries.

pkg/analyzer_cli/lib/src/build_mode.dart

 // Copyright (c) 2015, 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 analyzer_cli.src.build_mode;
 
 import 'dart:core' hide Resource;
 import 'dart:io' as io;
 
 import 'package:analyzer/dart/element/element.dart';
@@ skipping 68 matching lines @@
         if (!analysisResult.hasMoreWork) {
           break;
         }
       }
     }
 
     // Write summary.
     if (options.buildSummaryOutput != null) {
       PackageBundleAssembler assembler = new PackageBundleAssembler();
       for (Source source in explicitSources) {
-        if (context.computeKindOf(source) != SourceKind.LIBRARY) {
-          continue;
+        if (context.computeKindOf(source) == SourceKind.LIBRARY) {
+          if (options.buildSummaryFallback) {
+            assembler.addFallbackLibrary(source);
+          } else {
+            LibraryElement libraryElement = context.computeLibraryElement(source);
+            assembler.serializeLibraryElement(libraryElement);
+          }
         }
-        LibraryElement libraryElement = context.computeLibraryElement(source);
-        assembler.serializeLibraryElement(libraryElement);
+        if (options.buildSummaryFallback) {
+          assembler.addFallbackUnit(source);
+        }
       }
       // Write the whole package bundle.
       PackageBundleBuilder sdkBundle = assembler.assemble();
       if (options.buildSummaryExcludeInformative) {
         sdkBundle.flushInformative();
         sdkBundle.unlinkedUnitHashes = null;
       }
       io.File file = new io.File(options.buildSummaryOutput);
       file.writeAsBytesSync(sdkBundle.toBuffer(), mode: io.FileMode.WRITE_ONLY);
     }
@@ skipping 99 matching lines @@
             'Illegal input file (must be "\$uri|\$path"): $sourceFile');
         return null;
       }
       Uri uri = Uri.parse(sourceFile.substring(0, pipeIndex));
       String path = sourceFile.substring(pipeIndex + 1);
       uriToFileMap[uri] = new JavaFile(path);
     }
     return uriToFileMap;
   }
 }