Add support to extension_shell and ash_shell to use external V8 snapshot files.

gin/isolate_holder.cc

Index: gin/isolate_holder.cc
diff --git a/gin/isolate_holder.cc b/gin/isolate_holder.cc
index 317b5822bd8f47f773a0927d1a2b18ef6c2ebcb8..c9373e1ad369e4120a7ee3e30701663632ef6a31 100644
--- a/gin/isolate_holder.cc
+++ b/gin/isolate_holder.cc
@@ -7,6 +7,7 @@
 #include <stdlib.h>
 #include <string.h>
 
+#include "base/files/file.h"
 #include "base/files/memory_mapped_file.h"
 #include "base/logging.h"
 #include "base/message_loop/message_loop.h"
@@ -43,6 +44,43 @@ base::MemoryMappedFile* g_mapped_natives = NULL;
 base::MemoryMappedFile* g_mapped_snapshot = NULL;
 
 #if defined(V8_USE_EXTERNAL_STARTUP_DATA)
+#if !defined(OS_MACOSX)
+const int kV8SnapshotBasePathKey =
+#if defined(OS_ANDROID)
+    base::DIR_ANDROID_APP_DATA;
+#elif defined(OS_POSIX)
+    base::DIR_EXE;
+#elif defined(OS_WIN)
+    base::DIR_MODULE;
+#endif  // OS_ANDROID
+#endif  // !OS_MACOSX
+
+const char kNativesFileName[] = "natives_blob.bin";
+const char kSnapshotFileName[] = "snapshot_blob.bin";
+
+void GetV8FilePaths(base::FilePath* natives_path_out,
+                    base::FilePath* snapshot_path_out) {
+#if !defined(OS_MACOSX)
+  base::FilePath data_path;
+  PathService::Get(kV8SnapshotBasePathKey, &data_path);
+  DCHECK(!data_path.empty());
+
+  *natives_path_out = data_path.AppendASCII(kNativesFileName);
+  *snapshot_path_out = data_path.AppendASCII(kSnapshotFileName);
+#else   // !defined(OS_MACOSX)
+  base::ScopedCFTypeRef<CFStringRef> natives_file_name(
+      base::SysUTF8ToCFStringRef(kNativesFileName));
+  *natives_path_out =
+      base::mac::PathForFrameworkBundleResource(natives_file_name);
+  base::ScopedCFTypeRef<CFStringRef> snapshot_file_name(
+      base::SysUTF8ToCFStringRef(kSnapshotFileName));
+  *snapshot_path_out =
+      base::mac::PathForFrameworkBundleResource(snapshot_file_name);
+  DCHECK(!natives_path.empty());
+  DCHECK(!snapshot_path.empty());
+#endif  // !defined(OS_MACOSX)
+}
+
 bool MapV8Files(base::FilePath* natives_path,
                 base::FilePath* snapshot_path,
                 int natives_fd = -1,
@@ -117,45 +155,14 @@ extern const unsigned char g_natives_fingerprint[];
 extern const unsigned char g_snapshot_fingerprint[];
 #endif  // V8_VERIFY_EXTERNAL_STARTUP_DATA
 
-#if !defined(OS_MACOSX)
-const int IsolateHolder::kV8SnapshotBasePathKey =
-#if defined(OS_ANDROID)
-    base::DIR_ANDROID_APP_DATA;
-#elif defined(OS_POSIX)
-    base::DIR_EXE;
-#elif defined(OS_WIN)
-    base::DIR_MODULE;
-#endif  // OS_ANDROID
-#endif  // !OS_MACOSX
-
-const char IsolateHolder::kNativesFileName[] = "natives_blob.bin";
-const char IsolateHolder::kSnapshotFileName[] = "snapshot_blob.bin";
-
 // static
 bool IsolateHolder::LoadV8Snapshot() {
   if (g_mapped_natives && g_mapped_snapshot)
     return true;
 
-#if !defined(OS_MACOSX)
-  base::FilePath data_path;
-  PathService::Get(kV8SnapshotBasePathKey, &data_path);
-  DCHECK(!data_path.empty());
-
-  base::FilePath natives_path = data_path.AppendASCII(kNativesFileName);
-  base::FilePath snapshot_path = data_path.AppendASCII(kSnapshotFileName);
-#else  // !defined(OS_MACOSX)
-  base::ScopedCFTypeRef<CFStringRef> natives_file_name(
-      base::SysUTF8ToCFStringRef(kNativesFileName));
-  base::FilePath natives_path = base::mac::PathForFrameworkBundleResource(
-      natives_file_name);
-  base::ScopedCFTypeRef<CFStringRef> snapshot_file_name(
-      base::SysUTF8ToCFStringRef(kSnapshotFileName));
-  base::FilePath snapshot_path = base::mac::PathForFrameworkBundleResource(
-      snapshot_file_name);
-  DCHECK(!natives_path.empty());
-  DCHECK(!snapshot_path.empty());
-#endif  // !defined(OS_MACOSX)
-
+  base::FilePath natives_path;
+  base::FilePath snapshot_path;
+  GetV8FilePaths(&natives_path, &snapshot_path);
   if (!MapV8Files(&natives_path, &snapshot_path))
     return false;
 
@@ -194,6 +201,26 @@ bool IsolateHolder::LoadV8SnapshotFd(int natives_fd,
   return MapV8Files(
       NULL, NULL, natives_fd, snapshot_fd, natives_region, snapshot_region);
 }
+
+// static
+bool IsolateHolder::OpenV8FilesForChildProcesses(
+    base::PlatformFile* natives_fd_out,
+    base::PlatformFile* snapshot_fd_out) {
+  base::FilePath natives_data_path;
+  base::FilePath snapshot_data_path;
+  GetV8FilePaths(&natives_data_path, &snapshot_data_path);
+
+  int file_flags = base::File::FLAG_OPEN | base::File::FLAG_READ;
+  base::File natives_data_file(natives_data_path, file_flags);
+  base::File snapshot_data_file(snapshot_data_path, file_flags);
+
+  if (!natives_data_file.IsValid() || !snapshot_data_file.IsValid())
+    return false;
+
+  *natives_fd_out = natives_data_file.TakePlatformFile();
+  *snapshot_fd_out = snapshot_data_file.TakePlatformFile();
+  return true;
+}
 #endif  // V8_USE_EXTERNAL_STARTUP_DATA
 
 //static