Reland r17877 - Introduce a v8::Platform class that bundles embedder callbacks

src/v8.h

Index: src/v8.h
diff --git a/src/v8.h b/src/v8.h
index 01362ab972475dc0c808840401276c00340a50de..6f2633aa86522595f7a580b4af1197281dc1d9d3 100644
--- a/src/v8.h
+++ b/src/v8.h
@@ -50,6 +50,7 @@
 
 // Basic includes
 #include "../include/v8.h"
+#include "../include/v8-platform.h"
 #include "v8globals.h"
 #include "v8checks.h"
 #include "allocation.h"
@@ -111,6 +112,10 @@ class V8 : public AllStatic {
     array_buffer_allocator_ = allocator;
   }
 
+  static void InitializePlatform(v8::Platform* platform);
+  static void ShutdownPlatform();
+  static v8::Platform* GetCurrentPlatform();
+
  private:
   static void InitializeOncePerProcessImpl();
   static void InitializeOncePerProcess();
@@ -119,6 +124,8 @@ class V8 : public AllStatic {
   static List<CallCompletedCallback>* call_completed_callbacks_;
   // Allocator for external array buffers.
   static v8::ArrayBuffer::Allocator* array_buffer_allocator_;
+  // v8::Platform to use.
+  static v8::Platform* platform_;
 };