Reuse ZoneList memory if possible.

src/hydrogen-escape-analysis.cc

Index: src/hydrogen-escape-analysis.cc
diff --git a/src/hydrogen-escape-analysis.cc b/src/hydrogen-escape-analysis.cc
index 4eb2a13726a4dd5dd0bd84bfdfbaedfc1ba12a6d..831dd2f316e4a2eb0307ad4c748ca04193f3ba33 100644
--- a/src/hydrogen-escape-analysis.cc
+++ b/src/hydrogen-escape-analysis.cc
@@ -299,7 +299,7 @@ void HEscapeAnalysisPhase::PerformScalarReplacement() {
     int size_in_bytes = allocate->size()->GetInteger32Constant();
     number_of_values_ = size_in_bytes / kPointerSize;
     number_of_objects_++;
-    block_states_.Clear();
+    block_states_.Rewind(0);
 
     // Perform actual analysis step.
     AnalyzeDataFlow(allocate);
@@ -320,7 +320,7 @@ void HEscapeAnalysisPhase::Run() {
     CollectCapturedValues();
     if (captured_.is_empty()) break;
     PerformScalarReplacement();
-    captured_.Clear();
+    captured_.Rewind(0);
   }
 }