Allow startup with missing V8 snapshot file.

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"
@@ skipping 15 matching lines @@
                                         int* natives_size_out,
                                         const char** snapshot_data_out,
                                         int* snapshot_size_out);
 
 #if defined(V8_USE_EXTERNAL_STARTUP_DATA)
 
   // Load V8 snapshot from user provided platform file descriptors.
   // The offset and size arguments, if non-zero, specify the portions
   // of the files to be loaded. This methods returns true on success
   // (or if snapshot is already loaded), false otherwise.
-  static bool LoadV8SnapshotFromFD(base::PlatformFile natives_fd,
-                                   int64 natives_offset,
-                                   int64 natives_size,
-                                   base::PlatformFile snapshot_fd,
+  static bool LoadV8SnapshotFromFD(base::PlatformFile snapshot_fd,
                                    int64 snapshot_offset,
                                    int64 snapshot_size);
+  static bool LoadV8NativesFromFD(base::PlatformFile natives_fd,

[rmcilroy, 2015/06/01 14:06:31]

could you add WARN_UNUSED_RESULT on this (and possibly loadSnapshot if you
change it so it returns true when it fails in a way we expect).

[Erik Corry Chromium.org, 2015/06/02 11:18:52]

See below

+                                  int64 natives_offset,
+                                  int64 natives_size);
 
   // Load V8 snapshot from default resources. Returns true on success or
   // snapshot is already loaded, false otherwise.
   static bool LoadV8Snapshot();
 
+  // Load V8 natives source from default resources. Returns true on success or
+  // natives are already loaded, false otherwise.
+  static bool LoadV8Natives();

[rmcilroy, 2015/06/01 14:06:31]

WARN_UNUSED_RESULT here too.

[Erik Corry Chromium.org, 2015/06/02 11:18:52]

IT currently contains a LOG(FATAL) if it doesn't return true.  I think that's
better because a LOG might be more informative than a failed assert.  If we
stick with that, there's no point in having a return value.

[rmcilroy, 2015/06/02 11:27:07]

Right makes sense. OK, let's get rid of the return values for both 
LoadV8Natives and LoadV8Snapshot and just LOG(FATAL) within the functions if we
can't continue.

+
   // Opens the V8 snapshot data files and returns open file descriptors to these
   // files in |natives_fd_out| and |snapshot_fd_out|, which can be passed to
   // child processes.
   static bool OpenV8FilesForChildProcesses(base::PlatformFile* natives_fd_out,
                                            base::PlatformFile* snapshot_fd_out);
 
 #endif  // V8_USE_EXTERNAL_STARTUP_DATA
 };
 
 }  // namespace gin
 
 #endif  // GIN_V8_INITIALIZER_H_