Issue #2654 - Remove pre-allocated process manager.

Resolves #2654

layout/base/nsIPresShell.h

@@ -201,18 +201,6 @@ public:
 
   bool IsDestroying() { return mIsDestroying; }
 
-  /**
-   * Make a one-way transition into a "zombie" state.  In this state,
-   * no reflow is done, no painting is done, and no refresh driver
-   * ticks are processed.  This is a dangerous state: it can leave
-   * areas of the composition target unpainted if callers aren't
-   * careful.  (Don't let your zombie presshell out of the shed.)
-   *
-   * This is used in cases where a presshell is created for reasons
-   * other than reflow/painting.
-   */
-  virtual void MakeZombie() = 0;
-
   /**
    * All frames owned by the shell are allocated from an arena.  They
    * are also recycled using free lists.  Separate free lists are
@@ -1784,7 +1772,6 @@ protected:
   bool                      mStylesHaveChanged : 1;
   bool                      mDidInitialize : 1;
   bool                      mIsDestroying : 1;
-  bool                      mIsZombie : 1;
   bool                      mIsReflowing : 1;
 
   // For all documents we initially lock down painting.

layout/base/nsPresShell.cpp

@@ -1319,13 +1319,6 @@ PresShell::Destroy()
   mTouchManager.Destroy();
 }
 
-void
-PresShell::MakeZombie()
-{
-  mIsZombie = true;
-  CancelAllPendingReflows();
-}
-
 nsRefreshDriver*
 nsIPresShell::GetRefreshDriver() const
 {
@@ -3959,10 +3952,6 @@ PresShell::FlushPendingNotifications(mozFlushType aType)
 void
 PresShell::FlushPendingNotifications(mozilla::ChangesToFlush aFlush)
 {
-  if (mIsZombie) {
-    return;
-  }
-
   /**
    * VERY IMPORTANT: If you add some sort of new flushing to this
    * method, make sure to add the relevant SetNeedLayoutFlush or
@@ -6170,7 +6159,7 @@ PresShell::Paint(nsView*        aViewToPaint,
 
   MOZ_ASSERT(!mApproximateFrameVisibilityVisited, "Should have been cleared");
 
-  if (!mIsActive || mIsZombie) {
+  if (!mIsActive) {
     return;
   }
 
@@ -9024,10 +9013,6 @@ PresShell::ScheduleReflowOffTimer()
 bool
 PresShell::DoReflow(nsIFrame* target, bool aInterruptible)
 {
-  if (mIsZombie) {
-    return true;
-  }
-
   gfxTextPerfMetrics* tp = mPresContext->GetTextPerfMetrics();
   TimeStamp timeStart;
   if (tp) {

layout/base/nsPresShell.h

@@ -102,7 +102,6 @@ public:
   void Init(nsIDocument* aDocument, nsPresContext* aPresContext,
             nsViewManager* aViewManager, nsStyleSet* aStyleSet);
   virtual void Destroy() override;
-  virtual void MakeZombie() override;
 
   virtual void UpdatePreferenceStyles() override;