Adding V8 api to get memory statistics of spaces in V8::Heap.

src/api.cc

Index: src/api.cc
diff --git a/src/api.cc b/src/api.cc
index 14d3a823ebf637a75322e464704085812ab6dcb5..cfaa34ca7924c6d2c09b9fe202eb3520d5352cc3 100644
--- a/src/api.cc
+++ b/src/api.cc
@@ -5463,6 +5463,13 @@ HeapStatistics::HeapStatistics(): total_heap_size_(0),
                                   heap_size_limit_(0) { }
 
 
+HeapSpaceStatistics::HeapSpaceStatistics(): space_name_(0),
+                                            space_size_(0),
+                                            space_used_size_(0),
+                                            space_avalable_size_(0),
+                                            physical_space_size_(0) { }
+
+
 bool v8::V8::InitializeICU(const char* icu_data_file) {
   return i::InitializeICU(icu_data_file);
 }
@@ -7000,6 +7007,28 @@ void Isolate::GetHeapStatistics(HeapStatistics* heap_statistics) {
 }
 
 
+int Isolate::NumberOfHeapSpaces() {
+  return i::LAST_SPACE - i::FIRST_SPACE + 1;
+}
+
+
+bool Isolate::GetHeapSpaceStatistics(HeapSpaceStatistics* space_statistics,
+                                     int index) {
+  i::Isolate* isolate = reinterpret_cast<i::Isolate*>(this);
+  i::Heap* heap = isolate->heap();
+  if (index > i::LAST_SPACE || index < i::FIRST_SPACE || !space_statistics)

[rmcilroy, 2015/04/16 13:49:05]

nit - move the '!space_statistics' check out to a seperate if block (just for
code clarity).

[ssid, 2015/04/16 16:40:29]

Done.

+    return false;
+
+  space_statistics->space_name_ = heap->GetSpaceName(index);
+  space_statistics->space_size_ = heap->space(index)->CommittedMemory();

[rmcilroy, 2015/04/16 13:49:05]

nit - factor out:
 Space space = heap->space(index);
and use the 'space' local variable for these lookups to avoid having to call
space(index) multiple times.

[ssid, 2015/04/16 16:40:29]

Done.

+  space_statistics->space_used_size_ = heap->space(index)->Size();
+  space_statistics->space_avalable_size_ = heap->space(index)->Available();
+  space_statistics->physical_space_size_ =
+      heap->space(index)->CommittedPhysicalMemory();
+  return true;
+}
+
+
 void Isolate::GetStackSample(const RegisterState& state, void** frames,
                              size_t frames_limit, SampleInfo* sample_info) {
   i::Isolate* isolate = reinterpret_cast<i::Isolate*>(this);