[bindings] Migrate V8TestingScope out of V8Binding.h/cpp

Source/bindings/core/v8/V8Binding.h

Index: Source/bindings/core/v8/V8Binding.h
diff --git a/Source/bindings/core/v8/V8Binding.h b/Source/bindings/core/v8/V8Binding.h
index fc67cdac37c55fcae1444b9e4c6544b424fff8b3..0fe3c6d00bd8ebd0a0ade8e7063a1d8e4fa80d7b 100644
--- a/Source/bindings/core/v8/V8Binding.h
+++ b/Source/bindings/core/v8/V8Binding.h
@@ -999,19 +999,6 @@ private:
     v8::Isolate* m_isolate;
 };
 
-class V8TestingScope {
-public:
-    explicit V8TestingScope(v8::Isolate*);
-    ScriptState* scriptState() const;
-    v8::Isolate* isolate() const;
-    ~V8TestingScope();
-
-private:
-    v8::HandleScope m_handleScope;
-    v8::Context::Scope m_contextScope;
-    RefPtr<ScriptState> m_scriptState;
-};
-
 class DevToolsFunctionInfo final {
 public:
     explicit DevToolsFunctionInfo(v8::Handle<v8::Function>& function)