Move V8 snapshot loading code from isolate_holder to gin/v8_startup_data.{h,cc}.

gin/v8_initializer.h

+// Copyright 2013 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef GIN_V8_INITIALIZER_H_
+#define GIN_V8_INITIALIZER_H_
+
+#include "base/files/file.h"
+#include "gin/array_buffer.h"
+#include "gin/gin_export.h"
+#include "gin/public/v8_platform.h"
+#include "v8/include/v8.h"
+
+namespace gin {
+
+class GIN_EXPORT V8Initializer {
+ public:
+  // Controls whether or not V8 should only accept strict mode scripts.
+  enum ScriptMode { kNonStrictMode, kStrictMode };

[rmcilroy, 2015/03/30 10:29:22]

note for future cleanup (or now if it's easy) we should make this an "emum
class" now that we have C++11 compiler support.

[oth, 2015/03/30 15:55:19]

Yes, good point. In the near term, the code now just uses
gin::IsolateHolder::ScriptMode enum.

+
+  static const int kV8SnapshotBasePathKey;
+  static const char kNativesFileName[];
+  static const char kSnapshotFileName[];
+
+  // Should be invoked once before creating IsolateHolder instances to
+  // initialize V8 and Gin. In case V8_USE_EXTERNAL_STARTUP_DATA is defined,
+  // V8's initial snapshot should be loaded (by calling LoadV8Snapshot or
+  // LoadV8SnapshotFd) before calling Initialize.

[rmcilroy, 2015/03/30 10:29:22]

update "LoadV8SnapshotFd" in comment with name chosen below

[oth, 2015/03/30 15:55:19]

Done and comment moved to IsolateHolder.h for now.

+  static void Initialize(ScriptMode mode,
+                         v8::ArrayBuffer::Allocator* allocator);
+
+  static v8::ArrayBuffer::Allocator* GetArrayBufferAllocator();
+
+  static void GetV8ExternalSnapshotData(const char** natives_data_out,

[rmcilroy, 2015/03/30 10:29:22]

Could you document these methods please (you can copy the comments from
https://codereview.chromium.org/1019483002/diff/120001/gin/public/isolate_hol...)

[oth, 2015/03/30 15:55:19]

Done.

[oth, 2015/03/30 15:55:19]

Done.

+                                        int* natives_size_out,
+                                        const char** snapshot_data_out,
+                                        int* snapshot_size_out);
+
+#if defined(V8_USE_EXTERNAL_STARTUP_DATA)
+
+  static bool LoadV8SnapshotFromFile(base::PlatformFile natives_fd,

[rmcilroy, 2015/03/30 10:29:22]

Both this and LoadV8Snapshot load it from a file, so let's make this
LoadV8SnapshotFromFileDescriptor (or LoadV8SnapshotFromFD for succinctness) - 

[oth, 2015/03/30 15:55:19]

Done.

+                                     int64 natives_offset,
+                                     int64 natives_size,
+                                     base::PlatformFile snapshot_fd,
+                                     int64 snapshot_offset,
+                                     int64 snapshot_size);
+
+  static bool LoadV8Snapshot();
+
+#endif  // V8_USE_EXTERNAL_STARTUP_DATA
+};
+
+}  // namespace gin
+
+#endif  // GIN_V8_INITIALIZER_H_