Remove the dependency of Zone on Isolate

src/compiler.h

Index: src/compiler.h
diff --git a/src/compiler.h b/src/compiler.h
index 82b296a09968bd60f8e128850b77ca0d13e83048..bd9b98c74507cb0a887ce8d38dcfe6eb930ba6cf 100644
--- a/src/compiler.h
+++ b/src/compiler.h
@@ -529,21 +529,17 @@ class CompilationInfo {
 class CompilationInfoWithZone: public CompilationInfo {
  public:
   explicit CompilationInfoWithZone(Handle<Script> script)
-      : CompilationInfo(script, &zone_),
-        zone_(script->GetIsolate()) {}
+      : CompilationInfo(script, &zone_) {}
   explicit CompilationInfoWithZone(Handle<SharedFunctionInfo> shared_info)
-      : CompilationInfo(shared_info, &zone_),
-        zone_(shared_info->GetIsolate()) {}
+      : CompilationInfo(shared_info, &zone_) {}
   explicit CompilationInfoWithZone(Handle<JSFunction> closure)
-      : CompilationInfo(closure, &zone_),
-        zone_(closure->GetIsolate()) {}
+      : CompilationInfo(closure, &zone_) {}
   CompilationInfoWithZone(HydrogenCodeStub* stub, Isolate* isolate)
-      : CompilationInfo(stub, isolate, &zone_),
-        zone_(isolate) {}
+      : CompilationInfo(stub, isolate, &zone_) {}
   CompilationInfoWithZone(ScriptCompiler::ExternalSourceStream* stream,
                           ScriptCompiler::StreamedSource::Encoding encoding,
                           Isolate* isolate)
-      : CompilationInfo(stream, encoding, isolate, &zone_), zone_(isolate) {}
+      : CompilationInfo(stream, encoding, isolate, &zone_) {}
 
   // Virtual destructor because a CompilationInfoWithZone has to exit the
   // zone scope and get rid of dependent maps even when the destructor is