Magento improvement targeting FPC/block_html compatibility causing one cache storage access per layout block issue

fpc-block-html-optimize.patch

--- app/code/core/Mage/Core/Block/Abstract.php	2016-03-25 14:22:51.934883000 +0100
+++ app/code/local/Mage/Core/Block/Abstract.php	2016-03-25 14:39:53.806883000 +0100
@@ -1,4 +1,17 @@
 <?php
+/*
+ * Prevent unnecessary requests to cache storage on
+ *
+ * core_block_abstract_to_html_after
+ *
+ * due to
+ *
+ * enterprise_pagecache/observer::registerBlockTags
+ *
+ * calling $block->getCacheTags() on every block, with each block adding another cache storage request to fetch
+ * block tags for adding to cache tags for current FPC request in case particular block was pulled from block_html cache.
+ */
+
 /**
  * Magento Enterprise Edition
  *
@@ -1306,14 +1319,22 @@
     /**
      * Get tags array for saving cache
      *
+     * Inchoo: Lookup cache tags in cache storage only if block is block_html cacheable because
+     * only these blocks will have cache tags saved to cache storage to begin with (consult self::_saveCache).
+     *
      * @return array
      */
     public function getCacheTags()
     {
-        $tagsCache = $this->_getApp()->loadCache($this->_getTagsCacheKey());
-        if ($tagsCache) {
-            $tags = json_decode($tagsCache);
+        // Inchoo: START
+        if (!is_null($this->getCacheLifetime()) && $this->_getApp()->useCache(self::CACHE_GROUP)) {
+            $tagsCache = $this->_getApp()->loadCache($this->_getTagsCacheKey());
+            if ($tagsCache) {
+                $tags = json_decode($tagsCache);
+            }
         }
+        // Inchoo: END
+
         if (!isset($tags) || !is_array($tags) || empty($tags)) {
             $tags = !$this->hasData(self::CACHE_TAGS_DATA_KEY) ? array() : $this->getData(self::CACHE_TAGS_DATA_KEY);
             if (!in_array(self::CACHE_GROUP, $tags)) {