Optimize peak heap usage (#1858)

* asynchronous PackageGraph construction and precaching

* checkpoint

* cleanup

* checkpoint

* Run tools more asynchronously

* Enhacements and dropping of Future.wait

* dartfmt

* Rate-limit the number of tools in flight

* checkpoint

* Workaround for duplicate ResovledLibraryResult objects

* Patch up merge problem and rebuild test package docs

* Use maps to avoid having to filter results

* dartfmt and review comments

* Update test package docs again (quotation marks different in stable branch)

* Clear pubspec overrides (this will only work in sdk-analyzer Travis)

* Change sdk test branch to master (analyzer-0.33 not integrated yet)

* Set correct analyzer version

* Eliminate initialization race where analyzer might not find all the files in time for empty packages

* Update analyzer requirement

* Fix merge error

* Optimize peak heap usage

* Fix bug in library count

* Fix embedder and refactor file generation

* Review comments

Author: jcollins-g

lib/dartdoc.dart

@@ -115,15 +115,15 @@ class Dartdoc extends PackageBuilder {
 
     seconds = _stopwatch.elapsedMilliseconds / 1000.0;
     logInfo(
-        "Documented ${packageGraph.publicLibraries.length} public librar${packageGraph.publicLibraries.length == 1 ? 'y' : 'ies'} "
+        "Documented ${packageGraph.localPublicLibraries.length} public librar${packageGraph.localPublicLibraries.length == 1 ? 'y' : 'ies'} "
         "in ${seconds.toStringAsFixed(1)} seconds");
     return new DartdocResults(
         config.topLevelPackageMeta, packageGraph, outputDir);
   }
 
   Future<DartdocResults> generateDocs() async {
     DartdocResults dartdocResults = await generateDocsBase();
-    if (dartdocResults.packageGraph.publicLibraries.isEmpty) {
+    if (dartdocResults.packageGraph.localPublicLibraries.isEmpty) {
       throw new DartdocFailure(
           "dartdoc could not find any libraries to document");
     }