Share LibrarySpecificUnits when possible

pkg/analyzer/lib/src/context/context.dart

Index: pkg/analyzer/lib/src/context/context.dart
diff --git a/pkg/analyzer/lib/src/context/context.dart b/pkg/analyzer/lib/src/context/context.dart
index 858fd0636a60235d799a0f331834c973c7a6e256..c7488b2b615c3db10d8241c9f38810a39c83fd2d 100644
--- a/pkg/analyzer/lib/src/context/context.dart
+++ b/pkg/analyzer/lib/src/context/context.dart
@@ -644,6 +644,14 @@ class AnalysisContextImpl implements InternalAnalysisContext {
   }
 
   @override
+  AnalysisTarget canonicalizeTarget(AnalysisTarget target) {
+    if (target is LibrarySpecificUnit) {
+      return getLibrarySpecificUnit(target.library, target.unit);
+    }
+    return target;
+  }
+
+  @override
   String computeDocumentationComment(Element element) =>
       element?.documentationComment;
 
@@ -856,6 +864,7 @@ class AnalysisContextImpl implements InternalAnalysisContext {
   CacheEntry getCacheEntry(AnalysisTarget target) {
     CacheEntry entry = _cache.get(target);
     if (entry == null) {
+      target = canonicalizeTarget(target);
       entry = new CacheEntry(target);
       ImplicitAnalysisEvent event = null;
       if (target is Source) {
@@ -1007,6 +1016,22 @@ class AnalysisContextImpl implements InternalAnalysisContext {
       getResult(source, LIBRARY_ELEMENT);
 
   @override
+  LibrarySpecificUnit getLibrarySpecificUnit(Source library, Source unit) {
+    CacheEntry entry = analysisCache.get(unit);
+    if (entry != null) {
+      LibrarySpecificUnit lsu = entry.librarySpecificUnit;
+      if (lsu == null) {
+        lsu = new LibrarySpecificUnit(library, unit);
+        entry.librarySpecificUnit = lsu;
+        return lsu;
+      } else if (lsu.library == library && lsu.unit == unit) {
+        return lsu;
+      }
+    }
+    return new LibrarySpecificUnit(library, unit);
+  }
+
+  @override
   LineInfo getLineInfo(Source source) => getResult(source, LINE_INFO);
 
   @override