Expose a lower bound of malloc'd memory via heap statistics

src/crankshaft/compilation-phase.cc

Index: src/crankshaft/compilation-phase.cc
diff --git a/src/crankshaft/compilation-phase.cc b/src/crankshaft/compilation-phase.cc
index 375eb7ceec78b1898f023f7558aa31b1bfbe4df5..9b40ccaec462d76aacc6d7eeccb3c1951c9221c2 100644
--- a/src/crankshaft/compilation-phase.cc
+++ b/src/crankshaft/compilation-phase.cc
@@ -11,7 +11,7 @@ namespace v8 {
 namespace internal {
 
 CompilationPhase::CompilationPhase(const char* name, CompilationInfo* info)
-    : name_(name), info_(info) {
+    : name_(name), info_(info), zone_(info->isolate()->allocator()) {
   if (FLAG_hydrogen_stats) {
     info_zone_start_allocation_size_ = info->zone()->allocation_size();
     timer_.Start();