Add persistent handles to service protocol and Observatory UI

runtime/vm/dart_api_state.h

Index: runtime/vm/dart_api_state.h
diff --git a/runtime/vm/dart_api_state.h b/runtime/vm/dart_api_state.h
index 3c7d3165adb4f23f98945c5165af4b371623f7b2..b510377352cdc294d017c4922a86bd2e052e0c5f 100644
--- a/runtime/vm/dart_api_state.h
+++ b/runtime/vm/dart_api_state.h
@@ -213,6 +213,10 @@ class FinalizablePersistentHandle {
     return reinterpret_cast<Dart_WeakPersistentHandle>(this);
   }
 
+  intptr_t external_size() const {
+    return ExternalSizeBits::decode(external_data_);
+  }
+
   void SetExternalSize(intptr_t size, Isolate* isolate) {
     ASSERT(size >= 0);
     set_external_size(Utils::RoundUp(size, kObjectAlignment));
@@ -305,10 +309,6 @@ class FinalizablePersistentHandle {
     callback_ = callback;
   }
 
-  intptr_t external_size() const {
-    return ExternalSizeBits::decode(external_data_);
-  }
-
   void set_external_size(intptr_t size) {
     ASSERT(ExternalSizeBits::is_valid(size));
     external_data_ = ExternalSizeBits::update(size, external_data_);
@@ -445,6 +445,13 @@ class PersistentHandles : Handles<kPersistentHandleSizeInWords,
             kOffsetOfRawPtrInPersistentHandle>::VisitObjectPointers(visitor);
   }
 
+  // Visit all the handles.
+  void Visit(HandleVisitor* visitor) {
+    Handles<kPersistentHandleSizeInWords,
+            kPersistentHandlesPerChunk,
+            kOffsetOfRawPtrInPersistentHandle>::Visit(visitor);
+  }
+
   // Allocates a persistent handle, these have to be destroyed explicitly
   // by calling FreeHandle.
   PersistentHandle* AllocateHandle() {