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

test/cctest/test-platform-linux.cc

Index: test/cctest/test-platform-linux.cc
diff --git a/test/cctest/test-platform-linux.cc b/test/cctest/test-platform-linux.cc
index 34ae43c2081931d9740733f8e58a8cd11c13dba5..f289e948284cc1ec2f2e170b70c4063b289177c5 100644
--- a/test/cctest/test-platform-linux.cc
+++ b/test/cctest/test-platform-linux.cc
@@ -40,7 +40,6 @@ using namespace ::v8::internal;
 
 
 TEST(VirtualMemory) {
-  OS::SetUp();
   VirtualMemory* vm = new VirtualMemory(1 * MB);
   CHECK(vm->IsReserved());
   void* block_addr = vm->address();
@@ -55,6 +54,5 @@ TEST(VirtualMemory) {
 
 
 TEST(GetCurrentProcessId) {
-  OS::SetUp();
   CHECK_EQ(static_cast<int>(getpid()), OS::GetCurrentProcessId());
 }