Revert of Eagerly dispose of ScheduledActions. (patchset #2 id:20001 of...

Revert of Eagerly dispose of ScheduledActions. (patchset #2 id:20001 of https://codereview.chromium.org/2552673002/ )

Reason for revert:
Speculative revert for reported perf decrease on system_health.memory_mobile, https://crbug.com/672098

Original issue's description:
> Eagerly dispose of ScheduledActions.
>
> The DOMTimer's ScheduledAction hold on to the script source and
> state needed to execute the timer action. Let go of ShceduledAction's
> resource early.
>
> Apart from reducing the lifetime of script source, this is a speculative
> fix for crashes reported in v8::PersistentValueVector::Clear() during
> lazy sweeping of ScheduledAction objects.
>
> R=
> BUG=
>
> Committed: https://crrev.com/11bd50343795ed1dc1977da91e9a1588687522fd
> Cr-Commit-Position: refs/heads/master@{#436298}

TBR=oilpan-reviews@chromium.org,haraken@chromium.org
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=

Review-Url: https://codereview.chromium.org/2568103002
Cr-Commit-Position: refs/heads/master@{#437889}

third_party/WebKit/Source/bindings/core/v8/ScheduledAction.cpp

@@ -61,17 +61,7 @@ DEFINE_TRACE(ScheduledAction) {
   visitor->trace(m_code);
 }
 
-ScheduledAction::~ScheduledAction() {
-  // Verify that owning DOMTimer has eagerly disposed.
-  DCHECK(m_info.IsEmpty());
-}
-
-void ScheduledAction::dispose() {
-  m_code.dispose();
-  m_info.Clear();
-  m_function.clear();
-  m_scriptState.clear();
-}
+ScheduledAction::~ScheduledAction() {}
 
 void ScheduledAction::execute(ExecutionContext* context) {
   if (context->isDocument()) {

third_party/WebKit/Source/bindings/core/v8/ScheduledAction.h

@@ -56,8 +56,6 @@ class ScheduledAction final
   static ScheduledAction* create(ScriptState*, const String& handler);
 
   ~ScheduledAction();
-  void dispose();
-
   DECLARE_TRACE();
 
   void execute(ExecutionContext*);

third_party/WebKit/Source/bindings/core/v8/ScriptSourceCode.cpp

@@ -36,13 +36,6 @@ ScriptSourceCode::ScriptSourceCode(ScriptStreamer* streamer,
 
 ScriptSourceCode::~ScriptSourceCode() {}
 
-void ScriptSourceCode::dispose() {
-  m_source = String();
-  m_resource = nullptr;
-  m_streamer = nullptr;
-  m_url = KURL();
-}
-
 DEFINE_TRACE(ScriptSourceCode) {
   visitor->trace(m_resource);
   visitor->trace(m_streamer);

third_party/WebKit/Source/bindings/core/v8/ScriptSourceCode.h

@@ -56,7 +56,6 @@ class CORE_EXPORT ScriptSourceCode final {
   ScriptSourceCode(ScriptStreamer*, ScriptResource*);
 
   ~ScriptSourceCode();
-  void dispose();
   DECLARE_TRACE();
 
   bool isEmpty() const { return m_source.isEmpty(); }
@@ -66,13 +65,13 @@ class CORE_EXPORT ScriptSourceCode final {
   bool isNull() const { return m_source.isNull(); }
 
   const String& source() const { return m_source; }
-  ScriptResource* resource() const { return m_resource; }
+  ScriptResource* resource() const { return m_resource.get(); }
   const KURL& url() const;
   int startLine() const { return m_startPosition.m_line.oneBasedInt(); }
   const TextPosition& startPosition() const { return m_startPosition; }
   String sourceMapUrl() const;
 
-  ScriptStreamer* streamer() const { return m_streamer; }
+  ScriptStreamer* streamer() const { return m_streamer.get(); }
 
  private:
   void treatNullSourceAsEmpty();

third_party/WebKit/Source/core/frame/DOMTimer.cpp

@@ -107,10 +107,7 @@ DOMTimer::DOMTimer(ExecutionContext* context,
     startRepeating(intervalMilliseconds, BLINK_FROM_HERE);
 }
 
-DOMTimer::~DOMTimer() {
-  if (m_action)
-    m_action->dispose();
-}
+DOMTimer::~DOMTimer() {}
 
 void DOMTimer::stop() {
   InspectorInstrumentation::asyncTaskCanceled(getExecutionContext(), this);
@@ -118,8 +115,6 @@ void DOMTimer::stop() {
   // Need to release JS objects potentially protected by ScheduledAction
   // because they can form circular references back to the ExecutionContext
   // which will cause a memory leak.
-  if (m_action)
-    m_action->dispose();
   m_action = nullptr;
   SuspendableTimer::stop();
 }
@@ -177,8 +172,6 @@ void DOMTimer::fired() {
   executionContext->timers()->setTimerNestingLevel(0);
   // Eagerly unregister as ExecutionContext observer.
   clearContext();
-  // Eagerly clear out |action|'s resources.
-  action->dispose();
 }
 
 WebTaskRunner* DOMTimer::timerTaskRunner() const {