Report the reason for a garbage collection when verbose GC is enabled.

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 20 matching lines @@
     kNew,
     kOld,
     kCode,
   };
 
   enum ApiCallbacks {
     kIgnoreApiCallbacks,
     kInvokeApiCallbacks
   };
 
+  enum GCReason {
+    kNewSpace,
+    kPromotionFailure,
+    kOldSpace,
+    kCodeSpace,
+    kFull,
+    kGCAtAlloc,
+    kGCTestCase,
+  };
+
   // Default allocation sizes in MB for the old gen and code heaps.
   static const intptr_t kHeapSizeInMB = 512;
   static const intptr_t kCodeHeapSizeInMB = 12;
 
   ~Heap();
 
   uword Allocate(intptr_t size, Space space) {
     ASSERT(!read_only_);
     switch (space) {
       case kNew:
@@ skipping 86 matching lines @@
   void PrintSizes() const;
 
   // Returns the [lowest, highest) addresses in the heap.
   void StartEndAddress(uword* start, uword* end) const;
 
   ObjectSet* CreateAllocatedObjectSet() const;
 
   // Generates a profile of the current and VM isolate heaps.
   void Profile(Dart_HeapProfileWriteCallback callback, void* stream) const;
 
+  static const char* GCReasonToString(GCReason gc_reason);
+
  private:
   Heap();
 
   uword AllocateNew(intptr_t size);
   uword AllocateOld(intptr_t size);
   uword AllocateCode(PageSpace* space, intptr_t size);
 
   // The different spaces used for allocation.
   Scavenger* new_space_;
   PageSpace* old_space_;
@@ skipping 20 matching lines @@
  public:
   NoGCScope() {}
  private:
   DISALLOW_COPY_AND_ASSIGN(NoGCScope);
 };
 #endif  // defined(DEBUG)
 
 }  // namespace dart
 
 #endif  // VM_HEAP_H_