Store parts in Kernel Library, resynthesize parts in Analyzer.

runtime/vm/kernel_binary_flowgraph.h

Index: runtime/vm/kernel_binary_flowgraph.h
diff --git a/runtime/vm/kernel_binary_flowgraph.h b/runtime/vm/kernel_binary_flowgraph.h
index a9120ad8f7d3f570d65864d5bcf0e4f84461f7a4..bf5e4e64e5544c7159d1511f633a07787b1dd68b 100644
--- a/runtime/vm/kernel_binary_flowgraph.h
+++ b/runtime/vm/kernel_binary_flowgraph.h
@@ -414,6 +414,7 @@ class StreamingFlowGraphBuilder {
   void SkipVariableDeclaration();
   void SkipLibraryCombinator();
   void SkipLibraryDependency();
+  void SkipLibraryPart();
   void SkipLibraryTypedef();
   TokenPosition ReadPosition(bool record = true);
   void record_token_position(TokenPosition position);
@@ -1446,6 +1447,7 @@ class LibraryHelper {
     kSourceUriIndex,
     kAnnotations,
     kDependencies,
+    kParts,
     kTypedefs,
     kClasses,
     kToplevelField,
@@ -1493,6 +1495,13 @@ class LibraryHelper {
         }
         if (++next_read_ == field) return;
       }
+      case kParts: {
+        intptr_t part_count = builder_->ReadUInt();  // read list length.
+        for (intptr_t i = 0; i < part_count; ++i) {
+          builder_->SkipLibraryPart();
+        }
+        if (++next_read_ == field) return;
+      }
       case kTypedefs: {
         intptr_t typedef_count =
             builder_->ReadListLength();  // read list length.