add textblob cache freeall

src/gpu/GrTextBlobCache.cpp

Index: src/gpu/GrTextBlobCache.cpp
diff --git a/src/gpu/GrTextBlobCache.cpp b/src/gpu/GrTextBlobCache.cpp
index fe0ccf609899a15ebeb0238995ca63c1bf245042..d32e24bc1a3ddda0ce3828b003b6a6eef28ac353 100644
--- a/src/gpu/GrTextBlobCache.cpp
+++ b/src/gpu/GrTextBlobCache.cpp
@@ -10,11 +10,7 @@
 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,
@@ -48,3 +44,12 @@ GrAtlasTextContext::BitmapTextBlob* GrTextBlobCache::createBlob(int glyphCount,
 #endif
     return cacheBlob;
 }
+
+void GrTextBlobCache::freeAll() {
+    SkTDynamicHash<BitmapTextBlob, BitmapTextBlob::Key>::Iter iter(&fCache);
+    while (!iter.done()) {
+        (&(*iter))->unref();
+        ++iter;
+    }
+    fCache.rewind();
+}