Ensure external snapshot is only set once.

BUG=421063

Review URL: https://codereview.chromium.org/746263002

Cr-Commit-Position: refs/heads/master@{#25481}

src/api.cc

@@ -197,20 +197,12 @@ static inline bool IsExecutionTerminatingCheck(i::Isolate* isolate) {
 
 
 void V8::SetNativesDataBlob(StartupData* natives_blob) {
-#ifdef V8_USE_EXTERNAL_STARTUP_DATA
-  i::SetNativesFromFile(natives_blob);
-#else
-  CHECK(false);
-#endif
+  i::V8::SetNativesBlob(natives_blob);
 }
 
 
 void V8::SetSnapshotDataBlob(StartupData* snapshot_blob) {
-#ifdef V8_USE_EXTERNAL_STARTUP_DATA
-  i::SetSnapshotFromFile(snapshot_blob);
-#else
-  CHECK(false);
-#endif
+  i::V8::SetSnapshotBlob(snapshot_blob);
 }
 
 

src/v8.cc

@@ -18,10 +18,12 @@
 #include "src/hydrogen.h"
 #include "src/isolate.h"
 #include "src/lithium-allocator.h"
+#include "src/natives.h"
 #include "src/objects.h"
 #include "src/runtime-profiler.h"
 #include "src/sampler.h"
 #include "src/serialize.h"
+#include "src/snapshot.h"
 
 
 namespace v8 {
@@ -29,6 +31,11 @@ namespace internal {
 
 V8_DECLARE_ONCE(init_once);
 
+#ifdef V8_USE_EXTERNAL_STARTUP_DATA
+V8_DECLARE_ONCE(init_natives_once);
+V8_DECLARE_ONCE(init_snapshot_once);
+#endif
+
 v8::ArrayBuffer::Allocator* V8::array_buffer_allocator_ = NULL;
 v8::Platform* V8::platform_ = NULL;
 
@@ -117,4 +124,21 @@ v8::Platform* V8::GetCurrentPlatform() {
   return platform_;
 }
 
+
+void V8::SetNativesBlob(StartupData* natives_blob) {
+#ifdef V8_USE_EXTERNAL_STARTUP_DATA
+  base::CallOnce(&init_natives_once, &SetNativesFromFile, natives_blob);
+#else
+  CHECK(false);
+#endif
+}
+
+
+void V8::SetSnapshotBlob(StartupData* snapshot_blob) {
+#ifdef V8_USE_EXTERNAL_STARTUP_DATA
+  base::CallOnce(&init_snapshot_once, &SetSnapshotFromFile, snapshot_blob);
+#else
+  CHECK(false);
+#endif
+}
 } }  // namespace v8::internal

src/v8.h

@@ -82,6 +82,9 @@ class V8 : public AllStatic {
   static void ShutdownPlatform();
   static v8::Platform* GetCurrentPlatform();
 
+  static void SetNativesBlob(StartupData* natives_blob);
+  static void SetSnapshotBlob(StartupData* snapshot_blob);
+
  private:
   static void InitializeOncePerProcessImpl();
   static void InitializeOncePerProcess();