Fix --hydrogen-stats crashing on null_ptr for shared_info

BUG=

Review URL: https://codereview.chromium.org/1350293002

Cr-Commit-Position: refs/heads/master@{#30823}

src/compiler.h

@@ -294,7 +294,7 @@ class CompilationInfo {
   bool IsOptimizing() const { return mode_ == OPTIMIZE; }
   bool IsStub() const { return mode_ == STUB; }
   void SetOptimizing(BailoutId osr_ast_id, Handle<Code> unoptimized) {
-    DCHECK(!shared_info().is_null());
+    DCHECK(has_shared_info());
     SetMode(OPTIMIZE);
     osr_ast_id_ = osr_ast_id;
     unoptimized_code_ = unoptimized;

src/hydrogen.cc

@@ -13476,7 +13476,7 @@ void HTracer::FlushToFile() {
 
 
 void HStatistics::Initialize(CompilationInfo* info) {
-  if (info->shared_info().is_null()) return;
+  if (!info->has_shared_info()) return;
   source_size_ += info->shared_info()->SourceSize();
 }