Use fine-grained v8 headers in gin

Now that v8.h has been split into many parts, include only the parts
that are needed.

Bug: v8:11965
Change-Id: Id7557c588354a88533268d51f5fcdfc4fe29a733
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3122173
Commit-Queue: Leszek Swirski <[email protected]>
Auto-Submit: Dan Elphick <[email protected]>
Reviewed-by: Leszek Swirski <[email protected]>
Cr-Commit-Position: refs/heads/main@{#916424}
diff --git a/gin/v8_initializer.h b/gin/v8_initializer.h
index 2918c62..955be10 100644
--- a/gin/v8_initializer.h
+++ b/gin/v8_initializer.h
@@ -9,11 +9,15 @@
 
 #include "base/files/file.h"
 #include "base/files/memory_mapped_file.h"
+#include "build/build_config.h"
 #include "gin/array_buffer.h"
 #include "gin/gin_export.h"
 #include "gin/public/isolate_holder.h"
 #include "gin/public/v8_platform.h"
-#include "v8/include/v8.h"
+
+namespace v8 {
+class StartupData;
+}
 
 namespace gin {