Created methods to surface zone memory information for each isolate and thread in JSON.

runtime/vm/zone_test.cc

Index: runtime/vm/zone_test.cc
diff --git a/runtime/vm/zone_test.cc b/runtime/vm/zone_test.cc
index 4cb9231c74d539bd6486eff29c5adafbd536c833..cc53ebb658336b5bc7ceb52f02ec4c664633b0ee 100644
--- a/runtime/vm/zone_test.cc
+++ b/runtime/vm/zone_test.cc
@@ -169,4 +169,59 @@ TEST_CASE(PrintToString) {
   EXPECT_STREQ("Hello World!", result);
 }
 
+
+#ifndef PRODUCT
+UNIT_TEST_CASE(PrintZoneMemoryInfoToJSON) {
+#if defined(DEBUG)
+  FLAG_trace_zones = true;
+#endif
+  Dart_CreateIsolate(NULL, NULL, bin::isolate_snapshot_buffer, NULL, NULL,
+                     NULL);
+  Thread* thread = Thread::Current();
+  EXPECT(thread->zone() == NULL);
+  {
+    StackZone zone(thread);
+    StackZone string_stack_zone(thread);
+    EXPECT(thread->zone() != NULL);
+
+    intptr_t allocated_size = 0;
+    const intptr_t kNumElements = 1000;
+
+    zone.GetZone()->Alloc<uint32_t>(kNumElements);
+    allocated_size += sizeof(uint32_t) * kNumElements;
+
+    EXPECT_LE(allocated_size, zone.SizeInBytes());
+    {
+      JSONStream stream;
+      // Get the JSON formated zone information.
+      zone.GetZone()->PrintJSON(&stream);
+      const char* json = stream.ToCString();
+      // Ensure that  matches actual values.
+      char* size_buf = OS::SCreate(string_stack_zone.GetZone(),
+                                   "\"capacity\":%ld,"
+                                   "\"used\":%ld",
+                                   zone.SizeInBytes(), zone.UsedSizeInBytes());
+      EXPECT_SUBSTRING(size_buf, json);
+    }
+
+    // Expand the zone to ensure that JSON is updated accordingly.
+    zone.GetZone()->Alloc<uint32_t>(kNumElements);
+    allocated_size += sizeof(uint32_t) * kNumElements;
+    EXPECT_LE(allocated_size, zone.SizeInBytes());
+    {
+      JSONStream stream;
+      zone.GetZone()->PrintJSON(&stream);
+      const char* json = stream.ToCString();
+      char* size_buf = OS::SCreate(string_stack_zone.GetZone(),
+                                   "\"capacity\":%ld,"
+                                   "\"used\":%ld",
+                                   zone.SizeInBytes(), zone.UsedSizeInBytes());
+      EXPECT_SUBSTRING(size_buf, json);
+    }
+  }
+  EXPECT(thread->zone() == NULL);
+  Dart_ShutdownIsolate();
+}
+#endif
+
 }  // namespace dart