DartVM: Fix rounding error causing linear instead of geometric heap growth

runtime/vm/pages.cc

 // 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.
 
 #include "vm/pages.h"
 
 #include "platform/address_sanitizer.h"
 #include "platform/assert.h"
 #include "vm/compiler_stats.h"
 #include "vm/gc_marker.h"
@@ skipping 1231 matching lines @@
         const intptr_t limit = after.capacity_in_words +
                                (grow_heap_ * PageSpace::kPageSizeInWords);
         const intptr_t allocated_before_next_gc = limit - after.used_in_words;
         const double estimated_garbage = k * allocated_before_next_gc;
         if (t <= estimated_garbage / limit) {
           max = local_grow_heap - 1;
         } else {
           min = local_grow_heap + 1;
         }
       }
+      local_grow_heap = (max + min) / 2;
       grow_heap_ = local_grow_heap;
       ASSERT(grow_heap_ >= 0);
       // If we are going to grow by heap_grow_max_ then ensure that we
       // will be growing the heap at least by the growth ratio heuristics.
-      if ((grow_heap_ == heap_growth_max_) && (grow_ratio > grow_heap_)) {
-        grow_heap_ = grow_ratio;
+      if (grow_heap_ >= heap_growth_max_) {
+        grow_heap_ = Utils::Maximum(grow_ratio, grow_heap_);
       }
     }
   } else {
     heap_->RecordData(PageSpace::kGarbageRatio, 100);
     grow_heap_ = 0;
   }
   heap_->RecordData(PageSpace::kPageGrowth, grow_heap_);
 
   // Limit shrinkage: allow growth by at least half the pages freed by GC.
   const intptr_t freed_pages =
@@ skipping 27 matching lines @@
     return 0;
   } else {
     ASSERT(total_time >= gc_time);
     int result = static_cast<int>(
         (static_cast<double>(gc_time) / static_cast<double>(total_time)) * 100);
     return result;
   }
 }
 
 }  // namespace dart