add textblob cache freeall

src/gpu/GrTextBlobCache.cpp

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "GrTextBlobCache.h"
 
 static const int kVerticesPerGlyph = 4;
 
 GrTextBlobCache::~GrTextBlobCache() {
-    SkTDynamicHash<BitmapTextBlob, BitmapTextBlob::Key>::Iter iter(&fCache);
-    while (!iter.done()) {
-        (&(*iter))->unref();
-        ++iter;
-    }
+    this->freeAll();
 }
 
 GrAtlasTextContext::BitmapTextBlob* GrTextBlobCache::createBlob(int glyphCount, int runCount,
                                                                 size_t maxVASize) {
     // We allocate size for the BitmapTextBlob itself, plus size for the vertices array,
     // and size for the glyphIds array.
     size_t verticesCount = glyphCount * kVerticesPerGlyph * maxVASize;
     size_t size = sizeof(BitmapTextBlob) +
                   verticesCount +
                   glyphCount * sizeof(GrGlyph::PackedID) +
@@ skipping 13 matching lines @@
     }
     cacheBlob->fRunCount = runCount;
     cacheBlob->fPool = &fPool;
 
 #ifdef SK_DEBUG
     cacheBlob->fTotalXError = 0;
     cacheBlob->fTotalYError = 0;
 #endif
     return cacheBlob;
 }
+
+void GrTextBlobCache::freeAll() {
+    SkTDynamicHash<BitmapTextBlob, BitmapTextBlob::Key>::Iter iter(&fCache);
+    while (!iter.done()) {
+        (&(*iter))->unref();
+        ++iter;
+    }
+    fCache.rewind();
+}