Fix ref cnt'ing issue in GrProgramElement.

Drop ref on GrGpuResources when GrProgramElement loses its last ref and already has a pending execution.

BUG=skia:2889

Review URL: https://codereview.chromium.org/612293003

include/gpu/GrProgramElement.h

@@ -44,8 +44,12 @@ public:
     void unref() const {
         this->validate();
         --fRefCnt;
-        if (0 == fRefCnt && 0 == fPendingExecutions) {
-            SkDELETE(this);
+        if (0 == fRefCnt) {
+            if (0 == fPendingExecutions) {
+                SkDELETE(this);
+            } else {
+                this->removeRefs();
+            }
         }
     }
 
@@ -80,6 +84,8 @@ private:
 
     void completedExecution() const;
 
+    void removeRefs() const;
+
     mutable int32_t fRefCnt;
     // Count of deferred executions not yet issued to the 3D API.
     mutable int32_t fPendingExecutions;

src/gpu/GrProgramElement.cpp

@@ -31,9 +31,7 @@ void GrProgramElement::convertRefToPendingExecution() const {
     ++fPendingExecutions;
     this->unref();
     if (0 == fRefCnt) {
-        for (int i = 0; i < fGpuResources.count(); ++i) {
-            fGpuResources[i]->removeRef();
-        }
+        this->removeRefs();
     }
 }
 
@@ -53,3 +51,9 @@ void GrProgramElement::completedExecution() const {
         }
     }
 }
+
+void GrProgramElement::removeRefs() const {
+    for (int i = 0; i < fGpuResources.count(); ++i) {
+        fGpuResources[i]->removeRef();
+    }
+}