Revert "revert surfaceflinger leak fix as it uncovered a crasher on xoom"

This reverts commit af6edba59e250adbdfa5b3c3be134f70d8c38a16.

Change-Id: I7793d3ca8a4d20a2b188364f47854328ab5f586d

include/utils/RefBase.h

@@ -116,6 +116,20 @@ public:
 
     typedef RefBase basetype;
 
+    // used to override the RefBase destruction.
+    class Destroyer {
+        friend class RefBase;
+        friend class weakref_type;
+    public:
+        virtual ~Destroyer();
+    private:
+        virtual void destroy(RefBase const* base) = 0;
+    };
+
+    // Make sure to never acquire a strong reference from this function. The
+    // same restrictions than for destructors apply.
+    void setDestroyer(Destroyer* destroyer);
+
 protected:
                             RefBase();
     virtual                 ~RefBase();

libs/utils/RefBase.cpp

@@ -48,6 +48,11 @@ namespace android {
 
 // ---------------------------------------------------------------------------
 
+RefBase::Destroyer::~Destroyer() {
+}
+
+// ---------------------------------------------------------------------------
+
 class RefBase::weakref_impl : public RefBase::weakref_type
 {
 public:
@@ -55,7 +60,7 @@ public:
     volatile int32_t    mWeak;
     RefBase* const      mBase;
     volatile int32_t    mFlags;
-
+    Destroyer*          mDestroyer;
 
 #if !DEBUG_REFS
 
@@ -64,6 +69,7 @@ public:
         , mWeak(0)
         , mBase(base)
         , mFlags(0)
+        , mDestroyer(0)
     {
     }
 
@@ -310,7 +316,11 @@ void RefBase::decStrong(const void* id) const
     if (c == 1) {
         const_cast<RefBase*>(this)->onLastStrongRef(id);
         if ((refs->mFlags&OBJECT_LIFETIME_WEAK) != OBJECT_LIFETIME_WEAK) {
-            delete this;
+            if (refs->mDestroyer) {
+                refs->mDestroyer->destroy(this);
+            } else {
+                delete this;
+            }
         }
     }
     refs->removeWeakRef(id);
@@ -345,7 +355,9 @@ int32_t RefBase::getStrongCount() const
     return mRefs->mStrong;
 }
 
-
+void RefBase::setDestroyer(RefBase::Destroyer* destroyer) {
+    mRefs->mDestroyer = destroyer;
+}
 
 RefBase* RefBase::weakref_type::refBase() const
 {
@@ -369,16 +381,28 @@ void RefBase::weakref_type::decWeak(const void* id)
     if (c != 1) return;
     
     if ((impl->mFlags&OBJECT_LIFETIME_WEAK) != OBJECT_LIFETIME_WEAK) {
-        if (impl->mStrong == INITIAL_STRONG_VALUE)
-            delete impl->mBase;
-        else {
+        if (impl->mStrong == INITIAL_STRONG_VALUE) {
+            if (impl->mBase) {
+                if (impl->mDestroyer) {
+                    impl->mDestroyer->destroy(impl->mBase);
+                } else {
+                    delete impl->mBase;
+                }
+            }
+        } else {
             // LOGV("Freeing refs %p of old RefBase %p\n", this, impl->mBase);
             delete impl;
         }
     } else {
         impl->mBase->onLastWeakRef(id);
         if ((impl->mFlags&OBJECT_LIFETIME_FOREVER) != OBJECT_LIFETIME_FOREVER) {
-            delete impl->mBase;
+            if (impl->mBase) {
+                if (impl->mDestroyer) {
+                    impl->mDestroyer->destroy(impl->mBase);
+                } else {
+                    delete impl->mBase;
+                }
+            }
         }
     }
 }
@@ -502,8 +526,10 @@ RefBase::RefBase()
 
 RefBase::~RefBase()
 {
-    if (mRefs->mWeak == 0) {
-        delete mRefs;
+    if ((mRefs->mFlags & OBJECT_LIFETIME_WEAK) == OBJECT_LIFETIME_WEAK) {
+        if (mRefs->mWeak == 0) {
+            delete mRefs;
+        }
     }
 }