Add max post-gc heap usage metrics

runtime/vm/heap.h

 // Copyright (c) 2012, 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.
 
 #ifndef VM_HEAP_H_
 #define VM_HEAP_H_
 
 #include "platform/assert.h"
 #include "vm/allocation.h"
 #include "vm/flags.h"
@@ skipping 140 matching lines @@
                    intptr_t max_old_gen_words,
                    intptr_t max_external_words);
 
   // Verify that all pointers in the heap point to the heap.
   bool Verify(MarkExpectation mark_expectation = kForbidMarked) const;
 
   // Print heap sizes.
   void PrintSizes() const;
 
   // Return amount of memory used and capacity in a space, excluding external.
-  intptr_t UsedInWords(Space space) const;
-  intptr_t CapacityInWords(Space space) const;
-  intptr_t ExternalInWords(Space space) const;
+  int64_t UsedInWords(Space space) const;
+  int64_t CapacityInWords(Space space) const;
+  int64_t ExternalInWords(Space space) const;
   // Return the amount of GCing in microseconds.
   int64_t GCTimeInMicros(Space space) const;
 
   intptr_t Collections(Space space) const;
 
   ObjectSet* CreateAllocatedObjectSet(MarkExpectation mark_expectation) const;
 
   static const char* GCReasonToString(GCReason gc_reason);
 
   // Associate a peer with an object.  A non-existent peer is equal to NULL.
@@ skipping 41 matching lines @@
     stats_.times_[id] = micros;
   }
 
   void RecordData(int id, intptr_t value) {
     ASSERT((id >= 0) && (id < GCStats::kDataEntries));
     stats_.data_[id] = value;
   }
 
   bool gc_in_progress();
 
+  void UpdateGlobalMaxUsed();
+
   static bool IsAllocatableInNewSpace(intptr_t size) {
     return size <= kNewAllocatableSize;
   }
 
   void PrintToJSONObject(Space space, JSONObject* object) const;
 
   // The heap map contains the sizes and class ids for the objects in each page.
   void PrintHeapMapToJSONStream(Isolate* isolate, JSONStream* stream) {
     return old_space_.PrintHeapMapToJSONStream(isolate, stream);
   }
@@ skipping 128 matching lines @@
 // Note: During this scope, the code pages are non-executable.
 class WritableVMIsolateScope : StackResource {
  public:
   explicit WritableVMIsolateScope(Thread* thread);
   ~WritableVMIsolateScope();
 };
 
 }  // namespace dart
 
 #endif  // VM_HEAP_H_