Fix two leaks & improve leak tracking

src/lazy/SkLruImageCache.cpp

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkLruImageCache.h"
 
+SK_DEFINE_INST_COUNT(SkImageCache)
+SK_DEFINE_INST_COUNT(SkLruImageCache)
+
 static intptr_t NextGenerationID() {
     static intptr_t gNextID;
     do {
         gNextID++;
     } while (SkImageCache::UNINITIALIZED_ID == gNextID);
     return gNextID;
 }
 
 class CachedPixels : public SkNoncopyable {
 
@@ skipping 174 matching lines @@
         CachedPixels* pixels = iter.init(fLRU, Iter::kTail_IterStart);
         while (pixels != NULL && fRamUsed > limit) {
             CachedPixels* prev = iter.prev();
             if (!pixels->isLocked()) {
                 this->removePixels(pixels);
             }
             pixels = prev;
         }
     }
 }