Code re-factor related to WeakPtrFactory in src/gin module

Changing in the initialization order of WeakPtrFactory in src/gin module
such that all member variables should appear before the WeakPtrFactory
to ensure that any WeakPtrs to Controller are invalidated before its members
variable's destructor are executed, rendering them invalid.

BUG=303818

Review URL: https://codereview.chromium.org/580703002

Cr-Commit-Position: refs/heads/master@{#295709}

gin/modules/timer.cc

@@ -41,10 +41,10 @@ ObjectTemplateBuilder Timer::GetObjectTemplateBuilder(v8::Isolate* isolate) {
 
 Timer::Timer(v8::Isolate* isolate, bool repeating, int delay_ms,
              v8::Handle<v8::Function> function)
-    : weak_factory_(this),
-      timer_(false, repeating),
+    : timer_(false, repeating),
       runner_(PerContextData::From(
-          isolate->GetCurrentContext())->runner()->GetWeakPtr()) {
+          isolate->GetCurrentContext())->runner()->GetWeakPtr()),
+      weak_factory_(this) {
   GetWrapper(runner_->GetContextHolder()->isolate())->SetHiddenValue(
       GetHiddenPropertyName(isolate), function);
   timer_.Start(FROM_HERE, base::TimeDelta::FromMilliseconds(delay_ms),

gin/modules/timer.h

@@ -38,9 +38,10 @@ class GIN_EXPORT Timer : public Wrappable<Timer> {
   virtual ~Timer();
   void OnTimerFired();
 
-  base::WeakPtrFactory<Timer> weak_factory_;
   base::Timer timer_;
   base::WeakPtr<gin::Runner> runner_;
+  base::WeakPtrFactory<Timer> weak_factory_;
+
 };