Add max post-gc heap usage metrics

runtime/vm/scavenger.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_SCAVENGER_H_
 #define VM_SCAVENGER_H_
 
 #include "platform/assert.h"
 #include "platform/utils.h"
 #include "vm/dart.h"
@@ skipping 146 matching lines @@
     Scavenge();
     ASSERT(UsedInWords() == 0);
   }
 
   // Accessors to generate code for inlined allocation.
   uword* TopAddress() { return &top_; }
   uword* EndAddress() { return &end_; }
   static intptr_t top_offset() { return OFFSET_OF(Scavenger, top_); }
   static intptr_t end_offset() { return OFFSET_OF(Scavenger, end_); }
 
-  intptr_t UsedInWords() const {
+  int64_t UsedInWords() const {
     return (top_ - FirstObjectStart()) >> kWordSizeLog2;
   }
-  intptr_t CapacityInWords() const {
+  int64_t CapacityInWords() const {
     return to_->size_in_words();
   }
-  intptr_t ExternalInWords() const {
+  int64_t ExternalInWords() const {
     return external_size_ >> kWordSizeLog2;
   }
   SpaceUsage GetCurrentUsage() const {
     SpaceUsage usage;
     usage.used_in_words = UsedInWords();
     usage.capacity_in_words = CapacityInWords();
     usage.external_in_words = ExternalInWords();
     return usage;
   }
 
@@ skipping 78 matching lines @@
     end_ += sizeof(result);
     ASSERT(end_ <= to_->end());
     return result;
   }
   bool PromotedStackHasMore() const {
     ASSERT(scavenging_);
     return end_ < to_->end();
   }
 
   void UpdateMaxHeapCapacity();
+  void UpdateMaxHeapUsage();
 
   void ProcessWeakTables();
 
   intptr_t NewSizeInWords(intptr_t old_size_in_words) const;
 
   // Current allocation top and end. These values are being accessed directly
   // from generated code.
   uword top_;
   uword end_;
 
@@ skipping 26 matching lines @@
 
   friend class ScavengerVisitor;
   friend class ScavengerWeakVisitor;
 
   DISALLOW_COPY_AND_ASSIGN(Scavenger);
 };
 
 }  // namespace dart
 
 #endif  // VM_SCAVENGER_H_