Let blitters be notified when they're done being used

src/core/SkBlitter.cpp

Index: src/core/SkBlitter.cpp
diff --git a/src/core/SkBlitter.cpp b/src/core/SkBlitter.cpp
index cb84ec7d9db0aaa75f8539f7789fba8a5090bc70..b02f58864ef96fa1b0513471764b53c44daf0747 100644
--- a/src/core/SkBlitter.cpp
+++ b/src/core/SkBlitter.cpp
@@ -20,7 +20,12 @@
 #include "SkUtils.h"
 #include "SkXfermode.h"
 
-SkBlitter::~SkBlitter() {}
+SkBlitter::~SkBlitter() {
+    if (NULL != fBlitMemory) {
+        sk_free(fBlitMemory);
+        fBlitMemory = NULL;
+    }
+}
 
 bool SkBlitter::isNullBlitter() const { return false; }
 
@@ -193,6 +198,17 @@ void SkBlitter::blitMask(const SkMask& mask, const SkIRect& clip) {
     }
 }
 
+void* SkBlitter::allocBlitMemory(size_t sz) {
+    SkASSERT(NULL == fBlitMemory);
+    if (NULL != fBlitMemory) {
+        sk_free(fBlitMemory);
+        fBlitMemory = NULL;
+    }
+
+    fBlitMemory = sk_malloc_throw(sz);
+    return fBlitMemory;
+}
+
 /////////////////////// these guys are not virtual, just a helpers
 
 void SkBlitter::blitMaskRegion(const SkMask& mask, const SkRegion& clip) {