Introduce a RandonNumberGenerator class. Refactor the random/private_random uses in Isolate/Context.

src/platform.h

Index: src/platform.h
diff --git a/src/platform.h b/src/platform.h
index 6ae3fa00c0248e5237570b9152822d66ae7f877c..428ba55b2eef763e129082475d776fd452d9efce 100644
--- a/src/platform.h
+++ b/src/platform.h
@@ -86,11 +86,6 @@ inline int lrint(double flt) {
 
 #endif  // V8_CC_MSVC
 
-// Random is missing on both Visual Studio and MinGW.
-#if V8_CC_MSVC || V8_CC_MINGW
-int random();
-#endif  // V8_CC_MSVC || V8_CC_MINGW
-
 namespace v8 {
 namespace internal {
 
@@ -171,9 +166,6 @@ inline intptr_t InternalGetExistingThreadLocal(intptr_t index) {
 
 class OS {
  public:
-  // Initializes the platform OS support. Called once at VM startup.
-  static void SetUp();
-
   // Initializes the platform OS support that depend on CPU features. This is
   // called after CPU initialization.
   static void PostSetUp();